AGM vs Wet Lead Acid

[dbrock]

I have a 75Ah Platinum Prestige AGM battery under the driver's seat that has significantly deteriorated after 2 years and I am looking to replace it. It is currently giving around 30Ah and does not hold charge well if left idle for a few days. Should I get another like-for-like AGM or a wet Lead Acid?

The 240v charging is via a Sargent EC155 Power Supply Unit. I have heard mixed advice as to whether the Sargent can manage AGM cells adequately, or if they are better with wet Lead Acid batteries. The Sargent cannot manage a lithium cell. I would like to avoid a wet Lead Acid battery if possible due to ongoing maintenance. I would also like to avoid adding a new 240v charger if possible. It may be an upgrade in a couple of years.

The van is a T6 with a Smart Alternator and a Durite VSR split charge for the 12v leisure battery charging. I know VSR split chargers are not good with Smart Alternators, but I have heard that they can be adequate in the short-term. I need to keep the VSR for a while, but plan to replace it with a Victron Orion DC-DC charger. I also have a PV Logic MPPT Pro - Dual Battery Solar charge controller.

My requirements are to power a JKF50 fridge and cabin lights for 2 to 3 days. The spec on the fridge is a 0.7A draw and the lights can draw up to 0.6A. I measured the fridge power consumption and the maximum draw was about 2.6A. About 50Ah would be sufficient for me, so I am happy with a nominal 75Ah battery capacity. I can live with changing a battery after 2 years, as at that point I might be ready for a more comprehensive upgrade.

Any thoughts gratefully received.

 

[drinfinity]

Your AGM battery will only get to about 80% charge off the split charge relay, and then can only really discharge to about 50%. So getting around 30Ah is the top end of what you could expect.

With a reasonable Li battery and DCDC charge, you won’t need a 240V charger for your power draw for 3 days. I have a full camper conversion, 100Ah Li and DCDc with 100 W solar, and never needed to plug it in for long weekends.

 

[TrevorK]

If staying with AGM (I did), seek out an A rated leisure battery. The original battery fitted to my van was C class which is only designed for keeping the electrics running for a few hours.

 

[Qnapper]

Switched to LifePO4 battery and have never looked back. Loads of choice in the UK.

Worth a read before deciding

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[Dellmassive]

Upgrade to a lithium.

 

[dbrock]

Thanks for your advice. Looks like it is better to save money on a replacement battery and do the upgrade to lithium battery, DC-DC charger and a new 240v charger. I have read that I will need to deactivate the Sargent EC155 Power Supply Unit 240v charger. Is there anything fancy to doing that or do I simply remove the wires to the leisure battery and remove the fuse?

 

[Paul Sussex]

Think the charger only works if you switch the red button on top to ‘charge’ and connect ted to an EHU, otherwise it stays as a consumer unit only.

 

[Bigsidavies]

From your use case summary above you only require the LB for fridge and 12v lights. The Sargent charger is for 240v hookup. As you need a dc-dc charger anyway, and you already have solar with mppt (assuming this is lifepo compatable) then using a 105Ah lifepo will give you enough power for a weekend without the need for EHU. Therefore you could defer the expense of a new 240v charger until later, assuming you ever need one. I never use EHU, it only came in handy last year when my dc-dc stopped working on holiday. Having lifepo takes all the stress out of battery management and trying to guess when your agm battery is at 50%.
It is a no brainer. Take it from someone who had an AGM then went to lifepo.

 

[roadtripper]

I will need to deactivate the Sargent EC155 Power Supply Unit 240v charger. Is there anything fancy to doing that or do I simply remove the wires to the leisure battery and remove the fuse?

Don't remove wires as they are needed for the 12v distribution side of the EC155, on that model should be sufficient to pull the "charger" fuse which I think is 15A bottom right in the fusebox on the unit.

Very much support the suggestion to aim for a mid range LiFePo setup. As an interim step you could get yourself a Victron IP65 maintenance charger to keep the battery topped up rather than something fixed. You can get a quick connector and have that wired in at a suitable point to make it easier. That will help keep the battery topped up if you store your van for anything length of time and give you an option if you are out for longer periods camping. A lot of folks find that sufficient with the greater capacity of a LiFePo system.