Solar is boiling my batteries - possibly!

[skyflyer]

Before I installed solar I almost never had to top up the el trolyte levl on my two lead-acid batteries. Charging was done either through engine with an Adverc smart charge controller, or via shore power when available.

Last spring (2018) I innstalled a 100w panel with an Epever Tracer MPPT controller.

I now regularly have to top up the batteries. I’ve got through 2 litres of deionised water already this season.

The Epever manual details a charging regime that should end up in a “float charge” mode when left although it doesn’t specify how long each charge phase lasts prior to the float being applied. This is presumably to prevent boiling off the electrolyte. I tend to leave the boat for three to four weeks on a swinging mooring between visits. The batteries are always nicely charged on my return.

I’m wondering if the problem is a dc/dc charger I fitted between the no 1 battery which is charged directly from the solar MPPT and the no 2 battery which is only directly charged by engine or through shore power.

Could it be that whenever this kicks in, the MPPT cycle starts afresh thus giving too much bulk charge before going to float?

I’m trying to think how I can leave the boat to ensure both batteries benefit but without the boiling off that seems to be happening.

There is one other possibility. Since fitting the solar I have been more “cavalier” about depth of discharge, and although I never go below 50% I am less likely to top up the batteries with an engine run than I might have been before. Could this have an impact?

All ideas gratefully received.

 

[Mistroma]

It would be worth giving more detail on batteries (age, type, size, usage etc.) I couldn't see any details in your profile.

I usually add about 25-30mls per cell to my T105s every 6 weeks, so approx. 75-90mls per battery.
That would be around 300-400mls per battery over 6 months or around 1.2-1.6 litres in summer. I'm assuming that you don't have low maint. batteries (as you are adding water) and might be deep-cycle. Approx. 2 litres over 3 months does sound excessive for an average bank (say 300-500Ah).

What settings are you using on the Epever, mine has basic settings via the built in screen. The Tracer A manual details about 16 default settings for Sealed, Gel and Flooded.

It also has User defined settings and I can also alter a whole host of things from the remote panel (or via PC link if a panel is not installed).

User defined settings include:
Boost time
Equalisation time
Boost Voltage
Equalisation Voltage
High Voltage disconnect
Low Voltage Disconnect
Boost Voltage reconnect
and on and on and on, too many to list.

I configured the User defined settings because the default options didn't suit my usage for T105s. The "Flooded" defaults are actually reasonably close for T015s but possibly too high for some other "Flooded" types.

It is probably worth looking up the settings in the manual but I believe that the standard "Flooded" settings are probably:

Charging limit: 15.0V
Equalise: 14.8V (2 hours duration, default is once per month on 28th)
Boost: 14.6V (2 hours duration)
Float: 13.8V


The Epever Tracer retains the last max. and min. daily Voltages and I think that you should be able to see these via PC link. Might be worth checking but any unusually high Voltage could be from another charging source.

Two hours at 14.6V every day for 3-4 weeks when boat not being used might be excessive for your batteries which probably only need a float Voltage. You will also be getting one day with 14.8V as well. It is fine for me as I'm living on the boat, using power every day and then charging back to 100%.

 

[lw395]

These solar controllers are all really intended for non-boaty applications like signs and lights.
The design concept tends to be that there will be a significant load every night.
This tends to work out OK for liveaboards, but can cause issues for boats and caravans which are frequently unused for several daily cycles.
It can be helpful to understand exactly how the charging will cycle through, for example, a working week when the boat is only used at the weekend.
I am not familiar with that model of controller, but the above is the question I'd be trying to answer from the documentation.
Then you have to make the best of the available settings and then observe whether it's doing what you think it should be.

 

[KellysEye]

We had an Ampair wind generator and an on/off switch, we would keep an eye on the voltmeter and when the batteries were fully charged we turned the switch off,. The generator and switch were fitted by the previous owner who was shipwright.

 

[Mistroma]

We had an Ampair wind generator and an on/off switch, we would keep an eye on the voltmeter and when the batteries were fully charged we turned the switch off,. The generator and switch were fitted by the previous owner who was shipwright.

Not certain what you are suggesting, should OP:

1) Ditch solar and fit a wind-gen?
2) Replace Epever MPPT controller with an on/off switch?
3) Return to mooring mid-week to manually switch off charging once batteries are fully charged (from either wind or solar)?

I'm assuming you are suggesting all of the above or perhaps some combination.

 

[wiggy]

How about covering a large percentage of the panel when you leave the boat, would this be like having a little panel trickle charging your batteries?

 

[Mistroma]

How about covering a large percentage of the panel when you leave the boat, would this be like having a little panel trickle charging your batteries?

Or OP could just alter the settings on his excellent Epever MPPT unit.

 

[noelex]

The Epever manual details a charging regime that should end up in a “float charge” mode when left although it doesn’t specify how long each charge phase lasts prior to the float being applied.

The default absorption time is usually around two hours.

If leaving the boat with limited or no loads, it is worth reducing this adsorption time (if this an adjustable parameter for your controller). Most controllers start a new bulk/absorption cycle each day and two hours held at the absorption voltage is much too long if the batteries are fully or near fully charged.

It is also worth adjusting the float voltage in this situation. Not all battery manufacturers suggest the appropriate storage float voltage, but around 0.2-0.4V less than the cyclic float voltage is usually optimum.

 

[skyflyer]

Thanks. Funnily enough I had also thought of covering the panel. The problem is that I often leave the boat in a different state of discharge!

From what has been said it’s worth me investing in the necessary kit to be able to program my own charging regime into the Epever controller. The current (ha ha) float charge voltage is set to default 13.8v for flooded batteries. Also there is a defined time for boost charge os 120 minutes.

What I don’t want to do is end up messing up the charging when I am onboard when obviously I want to get the em imum benefit from the solar!

 

[noelex]

What I don’t want to do is end up messing up the charging when I am onboard when obviously I want to get the em imum benefit from the solar!

I can understand that.

Unfortunately, it is very difficult to have one set of charging parameters that works well in both situations.

If you don’t want to make changes when you store the boat, the best answer is to leave the settings as they are. This will overcharge the batteries when you are away, but this is better than undercharging the batteries when you are using the boat.

Personally, I like tweaking the settings, but providing you keep topping up the water, the improvement in battery life from this sort of adjustment is unlikely to be substantial.

 

[Mistroma]

Thanks. Funnily enough I had also thought of covering the panel. The problem is that I often leave the boat in a different state of discharge!

From what has been said it’s worth me investing in the necessary kit to be able to program my own charging regime into the Epever controller. The current (ha ha) float charge voltage is set to default 13.8v for flooded batteries. Also there is a defined time for boost charge os 120 minutes.

What I don’t want to do is end up messing up the charging when I am onboard when obviously I want to get the em imum benefit from the solar!

The MT50 makes it easy to modify the parameters. I can't remember if the Tracer A remembers User parameters. It would be easy and quick to switch between USER and FLOODED settings if it does. Just takes a little longer if it doesn't. I could probably check by altering my setup if you like.

I haven't tried the PC software but it should be cheaper than the MT50 remote as you only need a cable. I think the cable is just a USB to RS485 converter. I did buy a bare USB to RS485 unit for £2 or so on eBay but have never needed to cut up an RJ45 patch cable and wire it up to give USB at on end and RJ45 style connector at the other. It should be easy enough but could fritz the Epever if you don't know what you are doing.

The cable probably isn't too expensive but I seem to remember the standard one was 1.5m and a bit short.

It is possible that the PC software allows you to save and load saved configurations. I haven't looked at that but it would simplify matters for you. I seem to remember them also mentioning a smartphone app.

UPDATE:
I have just tried to switch between USER and FLOODED on MT50. It did not remember the USER settings and simply copied the current FLOODED settings. I had to put everything back manually. This means that the MT50 remote option will be a little fiddly.

Not a huge problem if you only change a few things (e.g. Boost time and Voltage plus float Voltage). Only takes 1-2 minutes once you are used to the menus. If you change too many things then you run into issues with logic for the 167 parameters (i.e. Some must be higher or lower than other related settings).

I couldn't find any detail on the PC software but it does use MDB format files and that means it stores something in a database. Reasonable chance of being able to switch configurations.

More information on your batteries would help. I suspect that settings could be lowered a bit with minimal impact on daily use and improve situation when just sitting on mooring fully charged.

 

[duncan99210]

It’s possible that the way the OP has his batteries wired with a battery to battery charger between the solar and his second battery. I’d be tempted to remove this charger temporarily and see if things improve.
I’ve got 220 watts of solar connected to my 500 amp hour domestic bank via a couple of generic controllers. The batteries are sealed ones, they remain connected all year round. We use the boat for four months live aboard during the summer, then it’s sits for the winter. Not had a problem with the system at all, the batteries settle down to about 13.6-8 volts over winter.

 

[skyflyer]

It’s not the cable that’s going to cost me it’s the PC! I’m on the dark side (Mac)! Although I do have a need for an old laptop with a parallel or serial port for something completely different so it’s not ruled out!

The batteries are from previous owner. 180ah flooded lead acid. No idea of what make or spec they are but I don’t think they’re anything special

Looking at the graphs on the charging regime in the manual, I think it wouldn’t make a huge difference to my day to day onboard charging if I reduced the float charge voltage from nominal 13.8v to something like 13.3v and reduced the boost time from 120mins to about 40.

This is on assumption that as discussed the controller restarts a new cycle every day and presumably whenever we start the engine and the controller then “sees” a battery voltage of 14.4v it has a fit and restarts when the engine shuts down.

With typically a minimum of two weeks, usually three, between visits to the boat it doesn’t need to be “top end” to recharge batteries fully by the time I return.

Most of the time when we are onboard the resting voltage of the batteries will be down to between 12.8v and 12.4v, less if there is a load being drawn, which gives the controller ample scope to pump in as much juice as it can.

For us solar is a finger in the dyke of electrical discharge, rather than a self sufficient source of power !

 

[noelex]

Looking at the graphs on the charging regime in the manual, I think it wouldn’t make a huge difference to my day to day onboard charging if I reduced the float charge voltage from nominal 13.8v to something like 13.3v and reduced the boost time from 120mins to about 40.

I dont think this is a good idea. Undercharging a lead acid battery is very bad for its lifespan. There is a likelihood that the settings you propose will do just that using the boat, and cycling the battery.

It may be possible to slightly reduce the absorption time. If you want to do this you need to check the battery return amps for a few cycles. This is complicated to explain (but I am happy to try if you are interested) and time consuming to check. However, even if this is done, any setting for cyclic use is likely to be way too long when the boat is not used. The reduction in water use and overcharging when the boat is left will be marginal unless very different settings for cyclic use and storage can be set.

The ideal absorption time is so different with the two usage patterns that a compromise is likely to be poor in both situations.

It sounds like the parameters on your solar controller are difficult and slow to change. Unfortunately, if it is not practical to alter the settings quickly and easily, the best solution is to stick with what you have. At least this will ensure reasonable charging when you are using the boat.

 

[ghostlymoron]

You don't say if the batteries are designated to start and house. 180 ahr sounds large for starting duty. If they are though you could ditch the B to B charger, have solar purely to 'house' and recharge the start with alternator only. If both are house batteries just wire them in parallel.

 

[[3889]]

I have an Epever MPPT and it works well on solar. However, if I connect to shore power I see my battery charging voltage rise to 14.6+. To stop this I disconnect the panel but I'm not sure why it happens in the 1st place.

 

[Chris_Robb]

I would consider only charging the House battery directly from the solar - and perhaps (if you have the space) add another battery so that you have a bank of 2 house batteries.

You could also add a small array of leds and set them to come on overnight on the dusk to dawn connection. This worked well with my set up on a steka mpm unit, after 2 years of coming back to the boat after winter and finding the batteries stuffed. In marmaris, the electricians did this as standard on all yachts with solar panels set up through the winter. It worked - and I checked out why with Bosche and they said this was essential to avoid constant over charging.

I now have a victron controller connected and it seems its clever enough to know that the batteries dont want any charge...... so I dont use the LEDs any more.

 

[skyflyer]

You don't say if the batteries are designated to start and house. 180 ahr sounds large for starting duty. If they are though you could ditch the B to B charger, have solar purely to 'house' and recharge the start with alternator only. If both are house batteries just wire them in parallel.

Yes its an irritating configuration from the boat manufactuter - two equally sized batteries and no dedicated start battery. My long term plan is to fit a smaller start battery and then parallel the two 180Ah into a single bank of house batteries.

But I'm not sure that changes the problem. The solar panel will still be going hell for leather into the house bank and if they are being overcharged they are being overcharged whether its one 180Ah or a 360Ah bank?

At the moment the battery that receives direct solar input is (was) lower on electrolyte than the other one that is charged by Dc to DC charger which does tehjd to imply that it is the solar input that is doing the damage.

I like the idea of a small load cycling on and off as per the set-up available on the Epever controller. But again its all bit of guesswork isnt it! How much power to take out of the battery vs how much will be put in, which depends how sunny it is and so on.

All in all I think the answer is KISS. Make sure the batteries are topped up with electrolyte as part of the leaving the boat and arriving at the boat routines.

 

[ghostlymoron]

I thought all charge controllers would stop charging at a preset voltage and sophisticated ones such as yours could be set to a voltage that would prevent damage to the battery.