Hi there. The time has come to change the batteries in our converted Transit. There are currently 2 x 70Ah Lead Acid Batteries but they just started to bubble and smoke which I’m guessing is a good indication that they should be changed! Lithium or AGM seems the way to go now but Lithium is not readily available where I live so I’m looking into the AGM options at the moment. I’ve come across 2 varieties. 1 ‘Start & Stop’ type and 1 ‘Deep Cycle’ type. I was told the 1st type is for the van engine and the 2nd type is for the utilities. Is this correct? Should I get 2 different types? Can’t I start the engine with the ‘Deep Cycle’ type and get 2 of those? Anyone with a good understanding of batteries out there to help me understand? Thanks. Mark
Greetings & Welcome!
This doesn’t sound right, lead acid batteries will normally bubble when being charged, but the smoking means you have other problems which should be sorted out.
Personally, I always wind up returning to lead acid deep cycle batteries. They are the most robust, forgiving, durable, and longest lasting. They are also the cheapest while being the most popular, tried, true, proven, & tested choice available.
My rigs all start extremely easily, so that allows me to be able to use a deep cycle battery as a starter battery too. I have 1x 100ah deep cycle house battery, and 1x 100ah deep cycle starter battery. Each will give me a weeks worth of power. I have low battery cut-offs on each battery to prevent them from being discharged past 50%. Even after the starter battery cuts off, it still has plenty of power to start my rig once reset.
I can’t say how well a deep cycle battery would work if your rig is harder to start…
Batteries 101: A start battery has multiple thin plates that produce a high current used to turn over starter motors. So it basically a big shot of electricity to turn the motor after a couple of big bursts they are discharged. Just like cranking a vehicle that won’t start 3-4 long cranks and click click click. A deep cycle has thick plates that deliver a low current for a long time as in using accessories. If you use a deep cycle for starting it will eventually damage the battery and a start battery will be damaged by long slow discharges. Then you have dual purpose which have medium size plate that can be used in both. Start batteries are measured in CCA cold cranking Amps. Deep cycles a measured in reserve minutes @ a 25 Amp load.
A regular “wet” battery is a plastic tub filled with liquid acid with the plates submerged in the acid bath. When you charge. Wet battery they vent toxic gas so they should not be used in a living space.
An AGM battery is the same concept but instead of the acid sloshing around it is absorbed in a fiberglass mat like a sponge that is between the plates. Then sealed in a plastic box. They do not vent and can be placed in any position like laying on its side. This is why they use AGMs in planes.
Gels are a whole different beast, can easily be overcharged. If you see a Gel or AGM that is bulging on the sides it has been overcharged.
An easy way to look a batteries is look at it as storing time. ………If you run a deep cycle @ 5 amp load for 10 hours it going to take a 5 amp charger 10 hours to put the “time” back in the box.
A 10 Amp charge would put the time back in 5 hours
A 20 Amp charge would put the time back in 2.5 hour.
If you charge too fast this will also damage the battery. This is why there a voltage regulators in vehicle alternators to limit the charge rate.
Thanks for your feedback. Very useful
Thank you for your feedback. Very informative
We went with lithium iron phosphate batteries and used Lion Energy batteries, which are always a great deal at Costco and ship very quickly and were one of the better prices for lithium batteries. I’d add a link, but it’s saying I cannot. Good luck with your decision!