Battery charging

[Rocksteadee]

Battery charging
Current set up:
Twin engine and diode splitters with alternator sensing on Aux battery side;
Dedicated start are wet LA batteries (14.7v);
Dedicated Aux are dual wet LA (14.7v), 50% capacity so knackered;
Victron 12/1600/70 compact multiplus with ‘start batt output’ to start batts. Output gives 14.4v 13.8v float) to aux but only 13.8v (13.2v float) to start batteries (undercharging);
Stand alone generator with start battery wet LA, with no float charging when not running.

Project:
Replace Aux batteries with deep cycle gel (14.4v);
Provide start and aux batteries with float charging on shore power
Provide a float charge and start link to genny batt.

Requirement:
3 charging scenarios to achieve correct voltages for each:
Cruising; at anchor with genny 1 to 2 hours twice daily; shore power.

Method:
Change both alternator sensing inputs to Start battery side of diode splitters to give 14.7v to start battery and 14.1v to Auxiliary battery (cruising);
Multiplus charger to Auxiliary battery only, set to 14.4v and disconnect start battery output (genny or shore power);
Add an additional 5A charger to start battery only, to give start battery a float charge when required (shore power);
Add a Cyrix combiner from start battery to genny battery to give a float charge and link starting if required (shore power as self charging when running)

Comments

 

[Hurricane]

Cruising; at anchor with genny 1 to 2 hours twice daily; shore power.

Comments

IMO, 1 to 2 hours twice daily works for about 3 days.
Talking about the house/service batteries here.
Using this (2 hour) regime, doesn't completely charge the batteries.
Initially, they will charge at a high current but, as we all know, that tapers off exponentially.
The reality is that using this 2 hour regime, they won't reach a fully charged state.
That generally requires a lot more hours.
The result is that you start your discharge cycle from a lower charged state each time.
Fine for a few days but this gradually creeps down until you reach that dangerous 50% charge state, eventually killing the batteries.

One solution is to run the generator longer but, like you, I like to keep my generator use to a minimum - especially in a nice anchorage.

I tried lots of ideas - AGMs - cheap batteries that didn't matter etc...

People will probably tell you to invest in Lithium but that is an expensive route.
I have the view that I could kill an expensive set of Lithiums just as easily as the cheaper lead acids.

In the end I fitted some solar panels.
Not enough to charge the batteries completely but enough to finish the charge cycle after the generator had done its 2 hours or so.
This has turned out to be a huge improvement.
I have then come "full circle" and now use good quality standard wet lead acid batteries.

The other advantage of solar panels is that they also work for "float charging" and provide that "backup" if the shore power becomes disconnected.

Hope that helps.

 

[PaulRainbow]

Battery charging
Current set up:
Twin engine and diode splitters with alternator sensing on Aux battery side;
Dedicated start are wet LA batteries (14.7v);
Dedicated Aux are dual wet LA (14.7v), 50% capacity so knackered;
Victron 12/1600/70 compact multiplus with ‘start batt output’ to start batts. Output gives 14.4v 13.8v float) to aux but only 13.8v (13.2v float) to start batteries (undercharging);

Not sure where you got the charging voltages, but they aren't correct. There are various options, but the default settings are :

Absortion 14.4V, float 13.8V and storage 13.2V

The starter battery output ( aux ) varies and is set to a 4A trickle charge. This does not usually undercharge the batteries, unless you leave them in a discharged state and have no other charging source.

Stand alone generator with start battery wet LA, with no float charging when not running.

Project:
Replace Aux batteries with deep cycle gel (14.4v);
Provide start and aux batteries with float charging on shore power
Provide a float charge and start link to genny batt.

Requirement:
3 charging scenarios to achieve correct voltages for each:
Cruising; at anchor with genny 1 to 2 hours twice daily; shore power.

Method:
Change both alternator sensing inputs to Start battery side of diode splitters to give 14.7v to start battery and 14.1v to Auxiliary battery (cruising);
Multiplus charger to Auxiliary battery only, set to 14.4v and disconnect start battery output (genny or shore power);
Add an additional 5A charger to start battery only, to give start battery a float charge when required (shore power);
Add a Cyrix combiner from start battery to genny battery to give a float charge and link starting if required (shore power as self charging when running)

Comments

It's late so i'll be brief. Gel batteries are expensive, i'd consider changing to Lithium. It's nothing like as expensive as it used to be. But, whatever batteries you fit, i agree with Hurricane, fit some solar.

 

[Rocksteadee]

IMO, 1 to 2 hours twice daily works for about 3 days.
Talking about the house/service batteries here.
Using this (2 hour) regime, doesn't completely charge the batteries.
Initially, they will charge at a high current but, as we all know, that tapers off exponentially.
The reality is that using this 2 hour regime, they won't reach a fully charged state.
That generally requires a lot more hours.
The result is that you start your discharge cycle from a lower charged state each time.
Fine for a few days but this gradually creeps down until you reach that dangerous 50% charge state, eventually killing the batteries.

One solution is to run the generator longer but, like you, I like to keep my generator use to a minimum - especially in a nice anchorage.

I tried lots of ideas - AGMs - cheap batteries that didn't matter etc...

People will probably tell you to invest in Lithium but that is an expensive route.
I have the view that I could kill an expensive set of Lithiums just as easily as the cheaper lead acids.

In the end I fitted some solar panels.
Not enough to charge the batteries completely but enough to finish the charge cycle after the generator had done its 2 hours or so.
This has turned out to be a huge improvement.
I have then come "full circle" and now use good quality standard wet lead acid batteries.

The other advantage of solar panels is that they also work for "float charging" and provide that "backup" if the shore power becomes disconnected.

Hope that helps.

Thanks for replying.
Understood about charging with genset.
Just to make my post clearer.
At anchor for only a few days then motor to a mooring with shore power.
Working on the principle of discharge to 50% and recharge after an hour on the gen in bulk charge to 80%. After an hour charger goes into absorption so charge current drops and gen/charge rate is progressively less efficient. Sometimes gen runs for 2 hours if cooking heating water etc.
This gives me 30% of battery capacity. 240Ah over 2 batteries is 72Ah, twice daily. 24hour boat consumption is about 100Ah.
144Ah charging is a bit short of the 100Ah doubled so looking at installing a 3rd 120Ah battery
360Ah x 30% gives 108Ah x 2 12hours = 216Ah. Usable capacity
This would mean upping charge from 48 to 72A to give safe charging current C/5. Then running gen for 1.5 hours to replace 108Ah.
Not concerned about only recharging to 80% as this is acceptable as after a few days motoring for a few hours then shore power to charge to 100%.
Have no space to fit solar.
Going for Gel batteries as they give most capacity for the space I have to fit them. And are only marginally more expensive than standard wet LA

 

[Rocksteadee]

Not sure where you got the charging voltages, but they aren't correct. There are various options, but the default settings are :

Absortion 14.4V, float 13.8V and storage 13.2V

The starter battery output ( aux ) varies and is set to a 4A trickle charge. This does not usually undercharge the batteries, unless you leave them in a discharged state and have no other charging source.



It's late so i'll be brief. Gel batteries are expensive, i'd consider changing to Lithium. It's nothing like as expensive as it used to be. But, whatever batteries you fit, i agree with Hurricane, fit some solar.

Hi Paul thanks for replying.
Got those voltages from a few places.
One was victon charge inv. manual

Gel: 14.4v max absorption 13.8v float 13.2v storage.
And here:
Google Search.

Wet: 14.7v, 13.8v, 13.2v respectively
And here:
Google Search

In my original post I only noted the max charge V and hadn’t included, as you correctely stated for float and standby.
My concern is the gel battery being sensitive to over charge.
When I checked the 4a aux output to start battery it was 0.6v lower than main output, as such when in storage start batt was being held at 12.7v which could possible lead to start of sulfation over winter.
Looked into lithium but couldn’t find anything to fit battery box which gave me the same capacity as Gel.
Have nowhere to put solar panels so can’t go that route.

If, as you say using 14.4v, this is within the range (14.4 to 14.7) for wet, I can charge both start wet LA and Gel aux batteries at 14.4v. Thus not needing the extra charger but join start and aux with a combiner relay, this also of having the advantage of giving me an emergency starting link

 

[PaulRainbow]

Hi Paul thanks for replying.
Got those voltages from a few places.
One was victon charge inv. manual

Gel: 14.4v max absorption 13.8v float 13.2v storage.
And here:
Google Search.

Wet: 14.7v, 13.8v, 13.2v respectively
And here:
Google Search

In my original post I only noted the max charge V and hadn’t included, as you correctely stated for float and standby.
My concern is the gel battery being sensitive to over charge.
When I checked the 4a aux output to start battery it was 0.6v lower than main output, as such when in storage start batt was being held at 12.7v which could possible lead to start of sulfation over winter.

This is normal. The 4A starter battery "trickle charge" isn't actually a true charger. It's a circuit that's connected to the Multplus DC input, it contains a current limiter and a diode. The diode causes a voltage drop of between about 0.3V and 0.6V, depending on the voltage of the domestic bank.

Looked into lithium but couldn’t find anything to fit battery box which gave me the same capacity as Gel.

You should be able to, i'm fitting 280Ah Lithium packs that are slightly smaller than a typical 110Ah lead acid battery. That's about 220Ah of usable Lithium against a usable 55Ah with LA. There are additional requirements, such as a BMS, DC-DC charger and different fuses, but Lithium can still be a very attractive solution, although not for everyone.

That said, if all you're concerned with is keeping the starter and genny battery safely charged Lithium might be overkill for you.

Have nowhere to put solar panels so can’t go that route.

That's a shame.

If, as you say using 14.4v, this is within the range (14.4 to 14.7) for wet, I can charge both start wet LA and Gel aux batteries at 14.4v. Thus not needing the extra charger but join start and aux with a combiner relay, this also of having the advantage of giving me an emergency starting link

The Multiplus will spend most of the Winter in storage mode @ 13.2V so the trickle charger will be 12.9V. If you disconnect the trickle charge and fit a Victron 120A Cyrix, it closes at 13V but you'll only be subjecting the starter battery to that voltage. The "Start assist" function might start your genny if the battery is a little discharged, but it's unlikely to start the engine as it has a max current rating of 120A and is wired with cables to suit that current, plus it's fused, so the current inrush from a big engine is likely to blow the fuse. I never connect the start assist wire. I fit a dedicated emergency switch. Finally, you'd need to fit two, one for the start engine and another for the genny.

So, If you aren't happy with the Victron trickle charge i'd suggest a second charger. Fit a small Victron IP22 charger 12/15/3 Blue Smart IP22 Charger - Victron Energy. Not a fortune more than a couple of Cyrix's

If you want emergency starting fit some on/off switches between the load terminals of the main isolators.

 

[Rocksteadee]

The Multiplus will spend most of the Winter in storage mode @ 13.2V so the trickle charger will be 12.9V. If you disconnect the trickle charge and fit a Victron 120A Cyrix, it closes at 13V but you'll only be subjecting the starter battery to that voltage. The "Start assist" function might start your genny if the battery is a little discharged, but it's unlikely to start the engine as it has a max current rating of 120A and is wired with cables to suit that current, plus it's fused, so the current inrush from a big engine is likely to blow the fuse. I never connect the start assist wire. I fit a dedicated emergency switch. Finally, you'd need to fit two, one for the start engine and another for the genny.

So, If you aren't happy with the Victron trickle charge i'd suggest a second charger. Fit a small Victron IP22 charger 12/15/3 Blue Smart IP22 Charger - Victron Energy. Not a fortune more than a couple of Cyrix's

If you want emergency starting fit some on/off switches between the load terminals of the main isolators.

Have drawn in a Cyrix to charge and link gen battery. For some reason I was looking at a 400A VSR, now looked at Cyrix and indeed it is 120A so good for charging but not link. Will poss look at a dedicated start battery charger which will give a degree of backup to main charger

 

[Hooligan]

IMO, 1 to 2 hours twice daily works for about 3 days.
Talking about the house/service batteries here.
Using this (2 hour) regime, doesn't completely charge the batteries.
Initially, they will charge at a high current but, as we all know, that tapers off exponentially.
The reality is that using this 2 hour regime, they won't reach a fully charged state.
That generally requires a lot more hours.
The result is that you start your discharge cycle from a lower charged state each time.
Fine for a few days but this gradually creeps down until you reach that dangerous 50% charge state, eventually killing the batteries.

One solution is to run the generator longer but, like you, I like to keep my generator use to a minimum - especially in a nice anchorage.

I tried lots of ideas - AGMs - cheap batteries that didn't matter etc...

People will probably tell you to invest in Lithium but that is an expensive route.
I have the view that I could kill an expensive set of Lithiums just as easily as the cheaper lead acids.

In the end I fitted some solar panels.
Not enough to charge the batteries completely but enough to finish the charge cycle after the generator had done its 2 hours or so.
This has turned out to be a huge improvement.
I have then come "full circle" and now use good quality standard wet lead acid batteries.

The other advantage of solar panels is that they also work for "float charging" and provide that "backup" if the shore power becomes disconnected.

Hope that helps.

Mike when at berth especially in the winter does the solar supplement the shore power or just act as a backup? I am wondering how many of the monthly kWh you get from solar vs shore power if you are on a trickle charge. I ask because as PE companies buy up marinas they understand what a profit centre utilities is in a marina and it is more of a stealth charge than a berthing fee which is quite visible.

 

[Hurricane]

Mike when at berth especially in the winter does the solar supplement the shore power or just act as a backup? I am wondering how many of the monthly kWh you get from solar vs shore power if you are on a trickle charge. I ask because as PE companies buy up marinas they understand what a profit centre utilities is in a marina and it is more of a stealth charge than a berthing fee which is quite visible.

Our electricity is included in our service charge (we own the berth - lease).
But I leave the solar panels connected to the house batteries when the boat is on her berth.
Not as an alternative - more as a backup to keep the batteries in good condition.
For example, I've just this morning moved the boat back to her berth from a month in the boatyard.
Whilst in the boatyard, the shore power failed (got water in one of the power leads.
Didn't worry me too much because the solar panels looked after the batteries whilst she was disconnected.
I always switch off my DC systems whilst I am away and so all my security cameras and routers etc run from shore power.
In that recent case, I got someone in the boatyard to sort out that power lead so that I could continue to monitor stuff from home.
I don't like loosing the connection to the boat when I'm at home - 3 cameras, PC and battery chargers etc all monitored remotely.

I could set it up using DC and using the solar panels if the shore power was ever disconnected.
But I'm not that brave!!!

 

[Rocksteadee]

So, If you aren't happy with the Victron trickle charge i'd suggest a second charger. Fit a small Victron IP22 charger 12/15/3 Blue Smart IP22 Charger - Victron Energy. Not a fortune more than a couple of Cyrix's

Hi Paul.
Now fitting IP22 12/20/3 charger which will cover start and genset batteries.
Can I check with you regarding AGB as I can fit 2 at 150Ah each.
Am aware they do not like too many PSOC but seeing as after 3 to 5 days at anchor then motoring for a few hours then on shore power there may only be slight shortening of life.
Still looking for Lithium but can’t find enough Ah for size of box (360 x 360j

 

[PaulRainbow]

Hi Paul.
Now fitting IP22 12/20/3 charger which will cover start and genset batteries.

Good choice.

Can I check with you regarding AGB as I can fit 2 at 150Ah each.
Am aware they do not like too many PSOC but seeing as after 3 to 5 days at anchor then motoring for a few hours then on shore power there may only be slight shortening of life.

It's best if you can keep the above 50%, but going down to 80% shouldn't shorten their life too much, assuming deep cycle batteries.

Still looking for Lithium but can’t find enough Ah for size of box (360 x 360j

So called "drop in" batteries consist of 4 cells (for a 12V battery) and a BMS in a plastic box. They often use cheap cells and/or a cheap BMS and the box wastes a lot of space. I make my own cell packs up and use a top quality BMS. A 280Ah cell pack is about 288mm x 174mm, so you'd have room for two. You can comfortably use 80%, so 224Ah each battery. 448 for two. They need putting together and the BMS fitting and setting up, so you'd need a decent local electrical person to do the job. You also need to consider charging them, you can't use the alternators without a DC-DC charger.

 

[jakew009]

I have the view that I could kill an expensive set of Lithiums just as easily as the cheaper lead acids.

Just on this point @Hurricane I have to strongly disagree.

We have literally thousands of 280Ah and 300Ah lithium (LFP) packs in solar CCTV towers across the UK.

We absolute rag the batteries discharging them from 100% to virtually 0% (they cut off at 10.8V) before swapping them out.
We buy decent cells but they are as cheap as anything else coming out of China.

We’ve yet to kill a battery and every time I test one on our CBA analyser, they normally still test more than their rated capacity.

You can use the full capacity of an LFP battery with no ill effects for 99% of use cases.

 

[Hurricane]

Just on this point @Hurricane I have to strongly disagree.

We have literally thousands of 280Ah and 300Ah lithium (LFP) packs in solar CCTV towers across the UK.

We absolute rag the batteries discharging them from 100% to virtually 0% (they cut off at 10.8V) before swapping them out.
We buy decent cells but they are as cheap as anything else coming out of China.

We’ve yet to kill a battery and every time I test one on our CBA analyser, they normally still test more than their rated capacity.

You can use the full capacity of an LFP battery with no ill effects for 99% of use cases.

OK - I take your point.
It was just my feeling - I have very little experience of Lithiums.
With all the additional considerations, an upgrade to Lithium is several times the cost of replacing Lead Acid so it would HAVE to work.
I suppose I was really judging my ability rather than the technology.

 

[PaulRainbow]

I have the view that I could kill an expensive set of Lithiums just as easily as the cheaper lead acids.

A 280Ah set of Lithium cells costs £260, that's a comfortable 240Ah

Cheap lead acid (not AGM, Gel or deep cycle) is about £100 for 110Ah, that's a usable 55Ah at 50% DoD.

The Lithium pack has 4.3 times the usable Ah of the cheap LA, 4.3 x £100 = £430 So your "cheap LA" actually costs almost double the price of Lithium.

Your initial installation would also need a BMS, a different fuse and a way of charging from the alternator, typically a DC-DC charger. Plus the cost of fitting, if you couldn't do it yourself. A properly installed system should require little to no user input and the BMS would make it very difficult for you to kill the batteries, it would be easier to kill LA.

Initial installation would therefore cost more, but not "several times more", but long term it would cost less, give more Ah and because of the faster rate of charge, even more power.

 

[simonfraser]

Just on this point @Hurricane I have to strongly disagree.

We have literally thousands of 280Ah and 300Ah lithium (LFP) packs in solar CCTV towers across the UK.

We absolute rag the batteries discharging them from 100% to virtually 0% (they cut off at 10.8V) before swapping them out.
We buy decent cells but they are as cheap as anything else coming out of China.

We’ve yet to kill a battery and every time I test one on our CBA analyser, they normally still test more than their rated capacity.

You can use the full capacity of an LFP battery with no ill effects for 99% of use cases.

Jake, what is the BMS failure rate on those packs ?

 

[jakew009]

Jake, what is the BMS failure rate on those packs ?

We use JBD BMS’s, failure rate is untracked but ~0%.

We have a serial connection to every battery and log its metrics every 5 minutes.