WheelchairDriver

I need to replace the battery in my Dodge Grand Caravan this week. It currently has a standard flooded battery.

Optima shows their yellow top AGM as being compatible with my vehicle.

I was wondering if a van's electrical system would damage an AGM battery? How do cars/vans regulate their voltages? Do they have charging profiles set, or do they just output a fixed voltage from the alternator?

The optima isnt a good choice not because it is AGM but because it is 55Ah. The SAME SIZED and equally deep cycle and starting capable Odyssey PC1500 is a better battery as its 68Ah so 20% bigger. And has higher cranking amps, as well. Same physical size. Also deep cycle capable.

The vans alternator puts out around 14.5V peak. Thats perfect for AGM. Since you cant drive long enough at that voltage to overcharge a battery anyway then it doesent need a "charge profile" as such. It simply holds the voltage high at 14.4 to 14.5V for hours. It does drop to a slightly lower 14.2V after its fully charged.

So all good.

Thanks for the alternator info.

My van's battery size is 94R or H7. Odyssey makes the Performance series in this size, but not the Extreme series, and I don't feel like measuring and researching what other sizes would fit.

It looks like the batteries this size at my local auto parts stores are all 80AH. The Optima Yellow has the better CCA and RC specs.

ODP-AGM94R

Is that case size.

Yes, 94R is the size.

No I mean search that term above, and odyssey, and you only see one battery. Its called odyssey ODP-AGM94R
https://www.gobatteries.co.uk/product/m ... 50-ln4-h7/


I will do it for you...
https://duckduckgo.com/?t=ffab&q=odysse ... 94R&ia=web

In that size the optima isnt too bad either. I thought that like my own crysler it used the group 34/78 size. In which the odyssey is substantially better than the optima. I used to sell both of them.

With either of those batteries you MUST periodically, every few months give a complete 101% charge. Say 24 tp 48 hours at 13.8V. And both gain from a charge voltage above 14.4V preferably 14.7V in cyclic use.

I see, got it.

Thanks for the charge topping off advice. I was planning on that when you mentioned the alternator voltages. All of my electric driving controls drain the battery some if I don't drive it for several days, especially noticeable during the winter. Because of this, I already have an Anderson on the front of my van to make maintaining/charging easy.

Me too. But the real solution was to add a 50 watt solar panel to the roof. And run it via a voltage regultor and an mppt solar gadget to the battery 24/7 set to 13.2v summer, 13.4v winter.

Its not enough in winter. Not enough daylight hours or sun too low in sky. So if I did it again I would use a 100w panel.

When I was at the store, the Odyssey was out of stock, so I went with the Yellow Top DH7.

By any chance do you have a spec sheet for the charging profile?

Constant current to 14.7v
Constant voltage until about an amp
Float voltage: 13.8?
Long term float voltage?
Temperature compensation, mV/C?

14.7V if recharging and in cyclic use gives best cycle life. The elevated voltage is needed to get that 101% returned in cyclic operation over a short recharge period. And in that case an 8 hour CV stage limit and a 1000th of C (so 30mA on a 30Ah batt) termination and no float needed.

In a car you are not hopefully deep cycling it so a day at 13.6V or 13.7 will achieve the same thing.

Long term maintainance at a low 13.2 to 13.3V needs no temperature compensation, as its just designed to keep it topped of and not allow any vehicle drain from dropping the voltage. Use 13.2 summer 13.3 winter. It will also charge a dead battery in around a week...

So it depends what you are doing with it.

Cyclic use 14.45 to 14.65V is perfect for 8 hours at CV (so initial CC time ignored) max or 1000thC whichever occurs first.
Or slower but safer if no hurry, end CV stage at say 0.7A and then float 13.6V For a day.

Or just set a supply to hold 13.3V indefinitely... And it will keep it full. No long term damage and best storage. I use an adjustable eBay 2A thing that takes almost no AC current to do that. For the price of a .
https://www.ebay.co.uk/itm/335746186174

FWIW, I just recently replaced the battery that was in my 2015 Dodge GC with an Odyssey - I forget the size offhand but the 94R sounds right... The battery I replaced was the one that was in it when I bought the van used so no idea of it's age or prior history... It was still starting fine, but I had a couple of issues that were causing me a lot of annoyance...

1. The cruise control wouldn't turn on until after I'd driven a couple of miles.

2. The lockdown for my chair would not release reliably... I called the company and the guy there says it is a problem he sees a lot, and it seems that almost every time it is 'cured' by replacing the battery... He also suggested that it would work better if I hit the release button as soon as I turned the van off, BEFORE hitting the door open button (this did help, though not 100%) His claim is that a marginal battery would have enough voltage sag from the load of opening the door that the release solenoid in the lockdown plate couldn't kick hard enough to trip the release.

When I got the battery 'tested' at the local oil quick change place they said it scored on the border between "good" and "replace"

I shopped around and found the same Odyssey battery was about USD $75 less from Amazon (free shipping because over their minimum price) so I got it from them, and got it installed with some help from friends at the Asylum... Both problems seem to have gone away, so the low voltage theory seems to have been correct...

ex-Gooserider