marine battery chargers are they worth the difference in price

Hi paul, the main reason is that i have access to a supply of partly used ex mercedez 80 AH car batteries . I dont run enough electrical items to add more than one but i wanted to run the new fridge i have just installed off this new battery so it didnt affect any of the other systems . i am experimenting with solar power as per my other posts to try to eventually be able to run the fridge without worrying about batteries running flat . in the past i only ever used to run the fridges on other boats i have had when the engine was running but i think fridges are perhaps a little more efficient than they used to be and i have adhered very carefully to installation guidelines re insulation etc . i will go away and look at the victron argofet thingy to also charge it from the alternator , thanks . just want to cover all bases really . solar , engine , shorepower .
 
pyrojames said:
Ignore their attitudes, .
Click to expand...
Going a bit further actually works really well, just had a count up - over half the posts on this thread are invisible. Just a few names added to the ignore list makes the day much more pleasant as you don't have the read anywhere near so much negative rude bickering and no downside really. Masses of experience on here, not just the grumpy-my way is the only way-know-it-all's. Most of which is given in a friendly generous manner.
Big thanks to the nice people :)

And for getting a bit of a hand to visualise what's going on (a bit) the water analogy might be useful to some =>

https://www.youtube.com/results?search_query=DC+Circuit+Water+Analogy
 
dunkelly said:
Hi paul, the main reason is that i have access to a supply of partly used ex mercedez 80 AH car batteries . I dont run enough electrical items to add more than one but i wanted to run the new fridge i have just installed off this new battery so it didnt affect any of the other systems . i am experimenting with solar power as per my other posts to try to eventually be able to run the fridge without worrying about batteries running flat . in the past i only ever used to run the fridges on other boats i have had when the engine was running but i think fridges are perhaps a little more efficient than they used to be and i have adhered very carefully to installation guidelines re insulation etc . i will go away and look at the victron argofet thingy to also charge it from the alternator , thanks . just want to cover all bases really . solar , engine , shorepower .
Click to expand...

There's no problem with that, run fridge of separate battery, fit a VSR, no problem charging dissimilar batteries, then later fit solar,

FET splitters still drop voltage at high current, can be twice as much as a VSR, so no improvement over say a Durite VSR which are cheaper

Brian
 
Hi Brian thanks for the durite suggestion ,seems like that is within my budget- still not sure what a vsr is but will look it up , i already have a 1,2 ,both switch , connecting the starter and 'old domestic' .As i said i have the 2nd domestic running the fridge and connected via an on/off battery switch just in case i ever need to top up the 1st domestic so i am thinking i should connect the vsr between the exsisting set and the new replacing the new switch i put in . does that make sense to you ?
 
dunkelly said:
Hi Brian thanks for the durite suggestion ,seems like that is within my budget- still not sure what a vsr is but will look it up , i already have a 1,2 ,both switch , connecting the starter and 'old domestic' .As i said i have the 2nd domestic running the fridge and connected via an on/off battery switch just in case i ever need to top up the 1st domestic so i am thinking i should connect the vsr between the existing set and the new replacing the new switch i put in . does that make sense to you ?
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Just connects between the terminals on your isolator, with a wire to earth. When the service battery is on charge, the relay closes and allows charge to your new battery, opens when you stop charging to isolate batteries.

Brian
 
ok i think i have got that, it is i think what i thought - replace the isolator to the new battery with the vsr , the negative is presumably just to activate the vsr so i leave the exsisting negative connected to the battery bank . having looked online i see fuses should be put on both positive connections , what size should these be? . if i may ,later i will try to draw up a rough schematic to run by you if thats ok .
 
dunkelly said:
ok i think i have got that, it is i think what i thought - replace the isolator to the new battery with the vsr , the negative is presumably just to activate the vsr so i leave the exsisting negative connected to the battery bank . having looked online i see fuses should be put on both positive connections , what size should these be? . if i may ,later i will try to draw up a rough schematic to run by you if thats ok .
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Fuses depend on cable size and loading, no reason why you cannot keep the isolator switch, use it for emergency engine start.

Brian
 
There's a good wiring diagram for the BEP VSR on their website. I would think that Durite have one as well. I had a problem with occasional 'chattering' when I fitted one but understand that the latest models don't suffer from this.
 
PaulRainbow said:
This isn't the first time this subject has been raised ;

http://www.ybw.com/forums/showthrea...-different-capacities-wired-in-parallel/page2

You will all note that the replies from a certain individual are somewhat different to the rudeness and trolling of this thread.

Post #15 might be of particular interest.
Click to expand...
I think that was the last time I posted on here, partly because of the way threads can be destroyed by pointless abuse and argument.

So let me add my comments based on this thread so far - starting with my post #15 from 2014: which answers this post.
lw395 said:
.....I'm not aware of any battery manufacturer advocating mixing capacities in a bank......
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Here us a real world example of why different capacities are OK.

Sabre yachts, who use Lifeline AGM batteries, regularly ship with different sizes to be able to get the maximum capacity from all the available space.

Lifeline were concerned by this but their research proved that a bank can be made up of different capacities and that the life of the batteries was not compromised, as long as they are all the same make and the same age. They accepted that his goes against most previous guidelines.

One way of achieving the largest bank for the available space is to change the starter battery for something very much smaller and use the space for another service battery. It is high cold cranking amps (CCA) that are needed to start an engine, not high Ah capacity. A 37Ah Red Flash or Odyssey AGMs can be less than half the size of a conventional starter battery but deliver very higher CCA. Mine has laid untouched on its side in the bilges for 10 years and always started my 56 HP Yanmar.

William_H said:
....The max capacity of the charger will dictate just how much charge you can get into a battery. Providing it produces more current than what is being used and natural losses in the battery a small charger will recharge a battery. (or bank of parallel batteries) just takes longer. So it might take a week to bring up a very low charged bank. ....
Click to expand...

The charger should be a maximum of about 20% of the battery capacity - that's 15% to charge the batteries and 5% to supply the loads, so a 400AH bank needs a (EDIT ) 100amp charger.

PaulRainbow said:
So you wouldn't recommend connecting two 185ah and one 75ah battery in parallel ?
Click to expand...

Connecting any combination in parallel is OK only for charging if the recommended absorption values are the same voltage. The batteries take only the amount of current they need so can't be overcharged unless the charge voltage is held for too long. The House battery must be charged first or the starter battery may get overcharged. If the starter battery is charged first then when a VSR closes and charges the house battery the starter may initially discharger hundreds of amps into a heavily depleted house bank. The VSR may then chatter on and off as the voltage on the starter bank falls rapidly.

Now let me add my new thoughts on all of this:

A proper marine shorepower is the best way to get the batteries to 100% but cheap car battery chargers should never be used on a boat for many reasons.

  1. It must have a high charge current to match the size of todays service batteries. A 400 Ah bank will need a charger that can deliver 100 amps.
  2. It should be a multi-stage charger that delivers a constant current up to a fixed absorption voltage then switches to a constant voltage charger, holding this voltage for a period (that should be user programable) and then drops down to a float voltage to prevent batteries being overcharged, even if the charger is permanently connected. This is the only way to charge a deep cycle service bank that may be many times the capacity of a starter battery.
  3. It must have a user programmable software setting to match the charger voltage exactly to any modern battery, not just switches for changing to Gel or AGM or FLA, even Lithium, as modern batteries all have different charging voltages.
  4. It should also have an external voltage sensor to measure the actual battery terminal voltage, there will be losses through cables, busbars and fuses, or a 1/2 both switch or a split diode that will cause a 0.7v drop.
  5. It should have a temperature sensor to measure the battery temperature and automatically adjust the charge voltage. This is especially important if the batteries are in the engine compartment or you are sailing in hot areas like the Med, where temperatures can get over 40C.
  6. You need a charger that is designed for safe marine use where the AC side is electrically insulated from the DC side to protect against stray currents that could kill swimmers in the water around the boat.
  7. You want a charger with a dedicated three pin plug, including an earth wire, or with wires that are clearly Live, Neutral and earth - not a two pin that could be plugged in with the Live and the Neutral reversed. This could also kill swimmers in the water around the boat.
 
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sailinglegend420 said:
I think that was the last time I posted on here, partly because of the way threads can be destroyed by pointless abuse and argument.

So let me add my comments based on this thread so far - starting with my post #15 from 2014: which answers this post.


Here us a real world example of why different capacities are OK.

Sabre yachts, who use Lifeline AGM batteries, regularly ship with different sizes to be able to get the maximum capacity from all the available space.

Lifeline were concerned by this but their research proved that a bank can be made up of different capacities and that the life of the batteries was not compromised, as long as they are all the same make and the same age. They accepted that his goes against most previous guidelines.

One way of achieving the largest bank for the available space is to change the starter battery for something very much smaller and use the space for another service battery. It is high cold cranking amps (CCA) that are needed to start an engine, not high Ah capacity. A 37Ah Red Flash or Odyssey AGMs can be less than half the size of a conventional starter battery but deliver very higher CCA. Mine has laid untouched on its side in the bilges for 10 years and always started my 56 HP Yanmar.



The charger should be a maximum of about 20% of the battery capacity - that's 15% to charge the batteries and 5% to supply the loads, so a 400AH bank needs a 10amp charger.



Connecting any combination in parallel is OK only for charging if the recommended absorption values are the same voltage. The batteries take only the amount of current they need so can't be overcharged unless the charge voltage is held for too long. The House battery must be charged first or the starter battery may get overcharged. If the starter battery is charged first then when a VSR closes and charges the house battery the starter may initially discharger hundreds of amps into a heavily depleted house bank. The VSR may then chatter on and off as the voltage on the starter bank falls rapidly.

Now let me add my new thoughts on all of this:

A proper marine shorepower is the best way to get the batteries to 100% but cheap car battery chargers should never be used on a boat for many reasons.

  1. It must have a high charge current to match the size of todays service batteries. A 400 Ah bank will need a charger that can deliver 100 amps.
  2. It should be a multi-stage charger that delivers a constant current up to a fixed absorption voltage then switches to a constant voltage charger, holding this voltage for a period (that should be user programable) and then drops down to a float voltage to prevent batteries being overcharged, even if the charger is permanently connected. This is the only way to charge a deep cycle service bank that may be many times the capacity of a starter battery.
  3. It must have a user programmable software setting to match the charger voltage exactly to any modern battery, not just switches for changing to Gel or AGM or FLA, even Lithium, as modern batteries all have different charging voltages.
  4. It should also have an external voltage sensor to measure the actual battery terminal voltage, there will be losses through cables, busbars and fuses, or a 1/2 both switch or a split diode that will cause a 0.7v drop.
  5. It should have a temperature sensor to measure the battery temperature and automatically adjust the charge voltage. This is especially important if the batteries are in the engine compartment or you are sailing in hot areas like the Med, where temperatures can get over 40C.
  6. You need a charger that is designed for safe marine use where the AC side is electrically insulated from the DC side to protect against stray currents that could kill swimmers in the water around the boat.
  7. You want a charger with a dedicated three pin plug, including an earth wire, or with wires that are clearly Live, Neutral and earth - not a two pin that could be plugged in with the Live and the Neutral reversed. This could also kill swimmers in the water around the boat.
Click to expand...

So do 400Ah need 10A or 100A charger? ..... 100A chargers are fookin expensive for a modest 400Ah. :eek: ... is 100A a typo?
 
sailinglegend420 said:
Connecting any combination in parallel is OK only for charging if the recommended absorption values are the same voltage. The batteries take only the amount of current they need so can't be overcharged unless the charge voltage is held for too long. The House battery must be charged first or the starter battery may get overcharged. If the starter battery is charged first then when a VSR closes and charges the house battery the starter may initially discharger hundreds of amps into a heavily depleted house bank. The VSR may then chatter on and off as the voltage on the starter bank falls rapidly.
Click to expand...

I was not going to reply, but must ask, do you know the theory behind a VSR ?

The VSR designed around the battery voltages, when first designed cut in was 13.55 volt, alternators back then were 13.6-13.8 volt regulation, drop out 12.9 volt, below the voltage of a flat battery on charge. Thus when linked you got a initial charge from the engine battery to the service battery, helping to reduce high shock loads on the alternator. But two things happen, engine battery voltage drops rapidly due to load taken, service battery rises quickly due to combined current from alternator and engine battery. If the battery is not dead flat, in theory 50% or above, voltage will settle above 12.9 volt, and service battery will take charge. Engine battery normally has a higher charge level, so needs a higher charge voltage so takes no charge till voltage reaches it's charge voltage. At this point the service battery is close to the capacity of the engine battery and both take a current as they need. There was a delay in switching to minimise chatter, while the switching voltages allowed for recharging the engine battery if it drops out at initial cut in.

Charging batteries is very involved and needs a scope to track actual current and voltages, not just what does the multimeter read.

If you click on this link http://www.kddpowercentre.co.uk/data/P4000_82_lit.pdf that is my 1982 litrature for the first full function VSR, charging, battery level indication and low voltage battery protection. If you read it things have not changed that much.

The above is not meant to be pointless abuse and argument.

Brian
 
GHA said:
http://www.smartgauge.co.uk/chargesize.html

Seems quite a sensible view on it.

Saying the best charger size is X is a bit like saying the best leg length for a pair of trousers is...... ;)

Lots of variables.
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One consideration not mentioned is how you use your boat, do you want to tie up, stuff as much as you can into the batteries, then cast off, or stay the night. One needs a relatively big amperage charger, the other can use a smaller charger and recharge while you sleep, as you are drawing little power.

As that site says, many ways, that actually includes switch-mode / transformer operation.

Brian
 
If your boat is full of '12V' gadgets you can need a reasonable size charger just to stay ahead of the fridge, lights, sound system etc. Other boats may find they don't have shore power often enough to justify spending lots more cash on a big battery charger.
 
Baggywrinkle said:
So do 400Ah need 10A or 100A charger? ..... 100A chargers are fookin expensive for a modest 400Ah. :eek: ... is 100A a typo?
Click to expand...
Sorry - a 400Ah needs about a 100Ah charger - that's 15% of AH capacity = 60 amps + 5% for house loads = 20 amps. Always go higher, so you need a 100 amps charger - I've never seen an 80 amp charger!!!!

AGMs need a minimum of 20% of Ah capacity +5% = 25%, so again = a 100A charger.

I have corrected my error.
 
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