AGM Leisure batteries, Advice please.

[TrevandJenny]

I have read with interest the various threads on batteries. April last year I replaced my single lead acid leisure battery with 2 x 100Ah AGM after obtaining advice the Sargent system charger would be suitable. After nearly 20 months installed it is.
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We have 100w solar panel, MH is stored away from overhead obstructions trees ect. They take and hold charge very well. I understand it is better to allow batteries to consume and recharge rather than left idle charging via S.P, Now to my question.
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By the side of the inner habitation step is a switched LED lamp, If I leave this LED lamp on when in storage would the current drawn be low enough to allow the S.P to keep the batteries topped up?? or would it not be suitable for the better maintenance of the batteries??
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All advice welcomed.

 

[Molly 3]

This time of year due to shading I get very little solar power from my 100w solar , the draw from sargent 328 is enough to very slowly drain the battery so a plug in required every few weeks, some say fit another SP ? I say 2 times nowt is still nowt .I fitted a cheap £25 Chinese battery monitor that counts amps in amps out and much more , it would also answer your question about current draw and state of charge in real time .

 

[Nick-Mandy]

I take it you mean 100watt solar panel, not 100amps

 

[Nick-Mandy]

Also, 100watt solar panel and 2 x 100Ah batteries, I think you'll need another solar panel to be worth while.

 

[TrevandJenny]

I take it you mean 100watt solar panel, not 100amps

Thanks brain cell error, Now corrected

 

[TrevandJenny]

Also, 100watt solar panel and 2 x 100Ah batteries, I think you'll need another solar panel to be worth while.

Last year we were away for months,all in the UK so not that sunny compared with nearer the equator, SP held up well, so far we have not had any battery or charging problems,
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I will check out the MH later this week, it has always been 14v plus when checked in storage, I was only concerned ref original post as not used MH much at all this year.

 

[Molly 3]

Last year we were away for months,all in the UK so not that sunny compared with nearer the equator, SP held up well, so far we have not had any battery or charging problems,
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I will check out the MH later this week, it has always been 14v plus when checked in storage, I was only concerned ref original post as not used MH much at all this year.

If it works for you great

 

[trevskoda]

200w of panels would be best and does it charge the engine start battery too, which if not best get it sorted when storing.

 

[Phantom]

By the side of the inner habitation step is a switched LED lamp, If I leave this LED lamp on when in storage would the current drawn be low enough to allow the S.P to keep the batteries topped up?? or would it not be suitable for the better maintenance of the batteries??
.
All advice welcomed.

I'd say that it should be just fine. Our 120w solar panel kept all of our batteries topped up during 5 months of storage last winter, started first touch.

 

[wildebus]

I would wonder why you would would want to leave a light on when in storage?

 

[TrevandJenny]

200w of panels would be best and does it charge the engine start battery too, which if not best get it sorted when storing.

I would love to fit another 100w panel, there seems little room on the roof to fit one. Thanks for your advice

I would wonder why you would would want to leave a light on when in storage?

I thought that by having a consumption IE the LED step light. it would be better for the batteries as they would discharge a little overnight then charge during the daylight, I realise dull days would be less than sunny days. Hence the suggestion of using LED step light thats drawing m-amps as they consume less and would require less charge.
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Assumption was discharge a little, charge via SP a little, Batteries doing what they should and not stagnating on a SP charge whilst in storage,

 

[Full Member]

I really don't think that you should worry about your batteries needing help to discharge, Trev.
ALL batteries discharge even when left initially charged but with no external electrical load. This effect is called 'self discharge' and varies depending on the battery chemistry, the quality of the chemicals used and the quality of the materials chosen to construct the battery.
I've copied this chart from wikipedia (I left a donation on our behalf!) which gives an indication of what to expect:

Battery chemistry	Rechargeable	Typical self-discharge or shelf life
Lithium metal	No	10 years shelf life[3]
Alkaline	No	5 years shelf life[3]
Zinc–carbon	No	2–3 years shelf life[3]
Lithium-ion	Yes	2–3% per month;[3] ca. 4% p.m.[4]
Lithium-polymer	Yes	~5% per month[5][better source needed]
Low self-discharge NiMH	Yes	As low as 0.25% per month[6]
Lead–acid	Yes	4–6% per month[3]
Nickel–cadmium	Yes	15–20% per month[3]
Nickel–metal hydride (NiMH)	Yes	30% per month[3]

As well as the self discharge mentioned above, in a real life system there will be other intended drains on the battery (e.g. monitoring circuits, alarm systems) and unintended electrical drains (e.g. electrical faults, poor design, low quality components).

As an example I have about 200Ah of good quality lead acid batteries installed in my Moho and am not using it at the moment.
Every 24 hours the batteries discharge due to the sum of the electrical losses (intended and non-intended) mentioned above. And then in the morning the 300W solar panel and solar charge controller recharges the battery to it's fully charged state.
For my system that means that the batteries are fully recharged in about 2 hours out of the 8.25 hours of charging time available at this time of the year.
As can be seen from the following data provided by the Victron charge controller, about 20Wh of energy are used and replaced every 24 hours even when the Moho is not in use . This equates to about 1.6 Ah or an average continual battery drain of about 0.065A (65mA).



For information, should your LED step light be about 1.5W, this would have a battery drain of about 0.12A (120mA).

In summary, you already have a drain on your battery whether intentional or not and in my view don't need to add a further electrical drain.
I hope this helps.

Colin

 

[TrevandJenny]

Colin, Many thanks for the chart and explanation of how the systems work, Several points you made I was unaware off, Mine runs fine with starting battery always 14v + as well as the leisure ones much the same.
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I was a bit concerned about them always on charge, your discharge explanation puts my mind at rest, Thank you.


Trev

 

[trevskoda]

I would love to fit another 100w panel, there seems little room on the roof to fit one. Thanks for your advice

I thought that by having a consumption IE the LED step light. it would be better for the batteries as they would discharge a little overnight then charge during the daylight, I realise dull days would be less than sunny days. Hence the suggestion of using LED step light thats drawing m-amps as they consume less and would require less charge.
.
Assumption was discharge a little, charge via SP a little, Batteries doing what they should and not stagnating on a SP charge whilst in storage,

A smart mppt regulator will run through a multi-stage charge cycle and float.

 

[Full Member]

Colin, Many thanks for the chart and explanation of how the systems work, Several points you made I was unaware off, Mine runs fine with starting battery always 14v + as well as the leisure ones much the same.
.
I was a bit concerned about them always on charge, your discharge explanation puts my mind at rest, Thank you.


Trev

Just one further point, Trev.
It's fine to leave batteries connected to a charger 24/7/365 providing that the charger is designed to do that.
You will have noted that the charger I show above has three charging stages. When it first starts charging it does so in what is called 'bulk charging' mode. The charge controller continues in this mode until it senses that the battery is pretty much fully charged then changes to what is called 'absorption charging' mode. Again, the charger continues in this mode until it senses that the battery is actually fully charged then changes to it's final mode known as 'float charging'. The charger stays in this final 'float charging' mode until the batteries have been discharged by more than a certain amount when the charger reverts to one of the earlier modes (usually 'bulk charging') and the process starts all over again.
It's important to note that not all chargers do this! Some (lower specification, usually lower cost) chargers keep charging in the 'bulk charging' or 'absorption charging' mode and do not sense that a battery is fully charged. This is likely to cause the battery to overheat and be wrecked, possibly in a very spectacular and dangerous manner!
The better chargers are generally called 'Intelligent' or similar. It's obviously best to check the charger specification but if you're not comfortable with that then do post here. There are plenty of helpful, knowledgeable folk waiting to help you. Don't be put off by any techno-gibberish. Any Moho related technical issue can be put in language that passes the Plain English 'Crystal Mark' - and, in my view, should be.
Again, I hope this helps.

Colin

 

[wildebus]

The following may (or may not?!) help illustrate with a picture Colins message above regarding the different charging modes that a good charger goes into. This is my own Motorhome from when I plugged in the charger yesterday and shows the various stages the charger goes into, and also the voltage at each stage. The charger in the graph below also has a 4th final mode which some chargers have and some do not - that being a 'storage' mode, where the voltage drops down again to a lower level again.

 

[Mr and Mrs Tupcox]

A smart mppt regulator will run through a multi-stage charge cycle and float.View attachment 57694

Thanks for posting this regulator been trying to find one ..now found on ebay little cheaper

 

[Molly 3]

The only time a battery should read 14 is when it is being charged it is a 12 v battery not 14 , YOU CAN ONLY GET A TRUE READING when no charge is going in , check after dark several hour after solar has stopped , a fully charged should read about 12 .8 volts .if it still reads high turn a a light the battery should drop down to about 12 . 7

 

[TrevandJenny]

Just one further point, Trev.
It's fine to leave batteries connected to a charger 24/7/365 providing that the charger is designed to do that.
You will have noted that the charger I show above has three charging stages. When it first starts charging it does so in what is called 'bulk charging' mode. The charge controller continues in this mode until it senses that the battery is pretty much fully charged then changes to what is called 'absorption charging' mode. Again, the charger continues in this mode until it senses that the battery is actually fully charged then changes to it's final mode known as 'float charging'. The charger stays in this final 'float charging' mode until the batteries have been discharged by more than a certain amount when the charger reverts to one of the earlier modes (usually 'bulk charging') and the process starts all over again.
It's important to note that not all chargers do this! Some (lower specification, usually lower cost) chargers keep charging in the 'bulk charging' or 'absorption charging' mode and do not sense that a battery is fully charged. This is likely to cause the battery to overheat and be wrecked, possibly in a very spectacular and dangerous manner!
The better chargers are generally called 'Intelligent' or similar. It's obviously best to check the charger specification but if you're not comfortable with that then do post here. There are plenty of helpful, knowledgeable folk waiting to help you. Don't be put off by any techno-gibberish. Any Moho related technical issue can be put in language that passes the Plain English 'Crystal Mark' - and, in my view, should be.
Again, I hope this helps.

Colin

Colin, Again thanks for the advice, yes indeed it helps. We have an Autosleeper broadway with factory fitted SP from new with Sargent electrics, as far as I can tell the SP regulator is within the Sargent box, Ive never touched it, weather it is intelligent version or not I cannot say, I spoke with Sargent prior to fitting the pair of AGM leisure batteries, they advised the system fitted to our MH was more than suitable for this application hence I fitted a pair of AGMs. It my well be I am concerned for nothing, I am from a mechanical background not electrical, I will leave it all well alone until it expires then look at increasing the watts on the roof by moving around the other items. Thanks everyone for the advice given.
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Trev

 

[TrevandJenny]

The only time a battery should read 14 is when it is being charged it is a 12 v battery not 14 , YOU CAN ONLY GET A TRUE READING when no charge is going in , check after dark several hour after solar has stopped , a fully charged should read about 12 .8 volts .if it still reads high turn a a light the battery should drop down to about 12 . 7

Molly, I must admit that I have never checked the MH after dark as it is in a controlled storage facility open loosely during daylight hours.
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Ref your theory of 14v when thinking of it, is 100% correct, I never thought of it that way, When I go to storage centre I never go on dull rainy days. So yes it always shows 14v, stupid me!!!, Thanks.

Trev