Battery Replacement in 2009 E4... EASIEST WAY

I need to replace batteries in my e4 and have no idea what the best/easiest way to get to those 2 rear batteries. I have a trunk on the back that will have to come off if I need to remove the spat ( which I have no idea how to do) but would give it a whirl… But of this “process” is [ol]
[/ol]too big of a pain in the ass …I guess I will just suck it up and take to dealer 1.5 hours drive from me. HELP … SUGGESTIONS.

Does anyone have a service manual for an 2009 E4?

Takes 10 minutes or less to remove the spat. Note the connections -/+ before disconnecting the batteries. Take pictures. Replace the batteries with the same type or you will have to reprogram the charger.


It has been awhile (2010) since I have seen it done but you have to remove the black plastic caps that cover the nuts that hold the spat on. They are just pushed onto the nuts underneath. Be careful not to scratch the car. Maybe use a flat standard screw driver and a cloth. There is a main wire harness connector that needs to be disconnected before you can move the loosened spat totally from the car. Then like was written before take photos, mark wires and don’t forget to turn off the main switch before you do anything. Safety first! Barry.:bullettrain_side:

Thx…I am looking for a place to get the 8g31 batteries online at best price… Suggestions?

On line doesn’t usually work too well because of shipping costs. Suggest Sams or Costco. Usually Batteries Plus isn’t too far off on price.

Try a local NAPA car part store. They sell gel batteries under their label that is made for them by the company Deka, that makes the original batteries supplied with the car. Barry🚄

I’m always a bit leary of this equivalency logic. I’ve worked in a different industry where the manufacturer made various items and private labelled them for others to sell. I can tell you with certainty that just because the same manufacturer made them they were NOT the same. The specs were all negotiated to various price points based on what the customer wanted. I don’t know about the battery industry but I suspect if the volume justified it NAPA could get DEKA to make them about anything they wanted as long as it was private labelled for NAPA.
This logic cuts both ways of course and OEM labelled gel batteries my be worse than NAPA too. That’s why new car tires rarely last very long.

Just my 2 cents.


Duplicate post

DEKA is made by EAST PENN Equal to or better than Trojan. I don’t buy anything else. Their private label batteries are made to their specs.

I respect you opinion and experience and won’t agree or disagree with you. Which battery is best probably depends a lot on the user of the battery and is quite subjective. I certainly don’t wish to start any flame wars on which brand is best. I’m certain we all have our own experiences to fall back on, we drive our GEMs differently and live in different parts of the world so I’d expect different results.

== Couple of other thoughts for consideration ==

I’m not sure how anyone could really tell absolutely which brand is “best” except perhaps in a lab with a test-to-destruction and even then there will be many variables that can influence the performance of a single battery. You’d need to test quite a few and average the results to get a meaningful conclusion.

Assuming the DEKA brand is manufactured and private labelled by East Penn for DEKA (and I certainly have no way of knowing), I will agree they are manufactured to DEKA specs. I would expect exactly that. Whether those specs and the resulting batteries are “better” than another brand is still pretty subjective I think.

Another assertion I’m somewhat wary of is attributing any private label as being manufactured by “Company X”. For me the problem w/ private labels is the label owner typically “shops” the specs around to get a better deal every so often. I’ve seen that in my former industry where this year the label owner would get items from one supplier and the next year, from a different supplier simply because they got better pricing. Big box stores do this all the time.

I personally use and recommend Trojan batteries. I readily admit they are expensive but I feel comfortable with them because Trojan batteries are manufactured by Trojan, have been around and used in industrial applications for a long time and everything I’ve seen or read seems to recommend them for this sort of deep discharge application. Though I’m equally sure someone will soon pipe up here with a negative experience with Trojan batteries which will at least demonstrate my point about subjective experiences!!


I have had both Deka and Napa. They have both performed the same. They were cheaper to me because the northern California AAA has a 10% off deal with Napa. Easy to find Napa dealers. I sold auto parts for years. Napa doesn’t sell cheap parts. I believe these private branded batteries are worth the look. I also buy Kenmore appliances branded by Sears and they also have been great. Tires are a different animal and are specified out differently as well as beds. Barry.

Perfect example with Kenmore. Used to be manufactured by Whirlpool and were pretty good I thought. Then they switched to another manufacturer (probably to save cost) and in my opinion the quality went down the toilet to the extent I won’t buy Kenmore any longer. And that’s exactly the problem I have with private labels and why I stay with brand names and pay a bit more for them. Just my personal opinion of course.


I asked Deka if the Napa branded batteries and the Deka 8g31 batteries with the Deka name were the same battery and they said they were the same. B.