Quirky solar vs alternator charging

[Rick-n-Jo]

I think  the effect you describe is as you suspect caused by temperature. I have had this to a much greater degree during a recent journey in the hot weather. Traction battery bank, instead of falling, the absorbtion current rose from 20A to over 40A while the battery temp climbed from mid 30s C to over 50c. Reading around a bit I learn, an LA batts ability to accept a charge falls as temp increases, the current instead just passing through, and presumably further heating the electrolyte. (Ultimately leading to thermal runaway??)

Had to restrict charge times for a few days to limit temp rise, now on shore power have been able to charge fully at a low current by using the shore current limiter facility on the Victron charger. Electrolyte temp now close to ambient and battery behavior back to normal, sitting on float at an amp or two.

 

If you can, a fan or blower to cool the engine space would be a good idea, or some insulation/reflective foil between engine and batts. Getting warm shortens the battery cycle life considerably.

[cuthound]

2 hours ago, Rick-n-Jo said:

I think  the effect you describe is as you suspect caused by temperature. I have had this to a much greater degree during a recent journey in the hot weather. Traction battery bank, instead of falling, the absorbtion current rose from 20A to over 40A while the battery temp climbed from mid 30s C to over 50c. Reading around a bit I learn, an LA batts ability to accept a charge falls as temp increases, the current instead just passing through, and presumably further heating the electrolyte. (Ultimately leading to thermal runaway??)

Had to restrict charge times for a few days to limit temp rise, now on shore power have been able to charge fully at a low current by using the shore current limiter facility on the Victron charger. Electrolyte temp now close to ambient and battery behavior back to normal, sitting on float at an amp or two.

 

If you can, a fan or blower to cool the engine space would be a good idea, or some insulation/reflective foil between engine and batts. Getting warm shortens the battery cycle life considerably.

 

Yes it could temperature related, especially if they are AGM's.

 

AGM's lose 50 of their life for every 5°C they are kept over 20°C (average temperature over a year), because the gas evolved during charging expands more at higher temperatures which causes the regulating valve to lift and vent the gas to atmosphere.

 

With AGM's the oxygen and hydrogen evolved during charging is recombine to make water for the electrolyte, so at high temperatures they vent electrolyte.

 

 

[Guest]

13 hours ago, Rick-n-Jo said:

I think  the effect you describe is as you suspect caused by temperature. I have had this to a much greater degree during a recent journey in the hot weather. Traction battery bank, instead of falling, the absorbtion current rose from 20A to over 40A while the battery temp climbed from mid 30s C to over 50c. Reading around a bit I learn, an LA batts ability to accept a charge falls as temp increases, the current instead just passing through, and presumably further heating the electrolyte. (Ultimately leading to thermal runaway??)

Had to restrict charge times for a few days to limit temp rise, now on shore power have been able to charge fully at a low current by using the shore current limiter facility on the Victron charger. Electrolyte temp now close to ambient and battery behavior back to normal, sitting on float at an amp or two.

 

If you can, a fan or blower to cool the engine space would be a good idea, or some insulation/reflective foil between engine and batts. Getting warm shortens the battery cycle life considerably.

Getting some ventilation into the battery/engine bay is definitely on my list of things to do. When I get a round tuit, it'll then be a case of deciding where the best place is to put it. 

[Guest]

On 09/07/2020 at 11:48, Rick-n-Jo said:

If you can, a fan or blower to cool the engine space would be a good idea, or some insulation/reflective foil between engine and batts. Getting warm shortens the battery cycle life considerably.

Thanks for the suggestion. Stuck some insulated reflective pipe wrap onto a board and stuck it between the engine and batteries and the charging figures seem more normal after cruising for a few hours today. Batteries feel a lot cooler too so fingers crossed they're happier. 

[Tony Brooks]

24 minutes ago, Rumsky said:

Thanks for the suggestion. Stuck some insulated reflective pipe wrap onto a board and stuck it between the engine and batteries and the charging figures seem more normal after cruising for a few hours today. Batteries feel a lot cooler too so fingers crossed they're happier. 

Thanks, That is interesting and maybe illustrates just how far away from normal we tend to operate our batteries.

 

Please let us know how it goes.