Noob battery question/identification

McNutty195

All,

I'm in the process of installing a battery monitor, and am trying to figure out what the capacity of my stock battery from the RV dealer is. I've looked through some of the posts on here and found some relevant information, but haven't been able to gather a full understanding yet.

The only ratings that I can find are CCA MCA and RC. I know these are Cold cranking amps, marine cranking amps, and reserve capacity respectively. I also looked up the model number and found some specs here. This lists the capacity as 81 Amp hours which already makes me sad. :(

So can any one please confirm for me, do I have a crappy, not really deep cycle battery that I should plan on replacing as soon as possible if I want to boondock with it?

Bonus question: So my capacity is 81 Amp hours, which I already think isn't all that great. How do I equate that to the measurements I get off of this battery monitor?

walker1477

Your battery is a $100 Interstate SRM-24 (just google "interstate SRM-24")

Group Size: 24DC
Part Number: SRM-24
Cold Cranking Amps: 550
Cranking Amps: 690
(RC) Min @ 25 Amp: 140
Amp Hours: 81
Length: 11
Width: 6 7/8
Height: 9 1/2
Weight: 46.3
Voltage: 12
Wet/Dry: W

HellFish

Didn't research your battery, so maybe it is a true deep cycle battery. Even if it is, 81 AH isn't much. But, you didn't mention what trailer you have and what electrical equipment, so that's about as detailed an answer as is possible. I now have a 105 AH true deep cycle battery on my 2014 T@G (it came with a crummy 67 AH battery). The Norcold is my energy hog, and 105 AH seems to be enough IF I have plenty of sun when boondocking. By that, I mean the battery gets me through the night and then the sun charges the battery up the next day. And so on...

I don't understand the bonus question, so somebody else gets those points.

McNutty195

@HellFish said:
Didn't research your battery, so maybe it is a true deep cycle battery. Even if it is, 81 AH isn't much. But, you didn't mention what trailer you have and what electrical equipment, so that's about as detailed an answer as is possible. I now have a 105 AH true deep cycle battery on my 2014 T@G (it came with a crummy 67 AH battery). The Norcold is my energy hog, and 105 AH seems to be enough IF I have plenty of sun when boondocking. By that, I mean the battery gets me through the night and then the sun charges the battery up the next day. And so on...

I don't understand the bonus question, so somebody else gets those points.

Yeah I agree that 81 AH isn't much. My understanding is that means only 40 AH is really usable without damaging the battery.

My setup is a 2018 T@G XL Outback edition. As of right now it is basically all stock, so I expect that the cooler will also be my primary power hog.

Sorry if I was confusing. I'm still new to this and trying to wrap my head around how the 12v system/battery works. My bonus question was asking how to equate the information I get from my battery monitor to how much battery capacity I have left. From what I've seen online it sounds like I basically just need to watch the current draw of each of my devices, as well as how long all of them are on and do the math myself. I was hoping that the WH measurement on the battery monitor would tell me, and I feel like I should be able to just take 81 AH * 12V to get ~970 WH of total battery capacity. However I'm not sure if that is really accurate or how it works.

tagurit

Same battery that came with our 2017 T@G and still there. Did at least 12,000 miles last year including one 24 day trip with the Norcold on 24/7 and never had a problem, battery charged by TV when driving and when at occasional campsite with hook ups, have solar but seldom have needed it.

McNutty195

@tagurit

Good to know! Maybe the battery will be less of a problem that I initially thought.

Fourman110

I had that one in mine from Jerry's in Madison. Ended up being a poor performer and replaced with two 6V golf cart batteries.

tagurit

We seldom boondock for more than a day or two and the standard battery plus solar panel works for us. We're glad it does because we are dedicated MINI maniacs and both our MINIs only have class I hitches available. We've already pulled the propane off the tongue to allow more cargo, no way do we want to add back 140 pounds or so of 6 volt batteries.

McNutty195

@tagurit

I'll have to see how it does for my wife and I. I noticed the mini in your profile picture. Was wondering about that a little. Never really thought of something like a mini towing, though upon a little extra looking, apparently they can tow quite a bit more than our CRV depending on the model. Who knew! lol Well besides you of course.

tagurit

MINI USA doesn't even talk about towing although OE towing accessories are available in Europe. There, our Countryman is rated for 3300 lbs and our convertible 1500.

BBsGarage

@tagurit said:
MINI USA doesn't even talk about towing although OE towing accessories are available in Europe. There, our Countryman is rated for 3300 lbs and our convertible 1500.

Probably because we have more lawyers than common sense here in the US.

Nfallon

@tagurit said:
Same battery that came with our 2017 T@G and still there. Did at least 12,000 miles last year including one 24 day trip with the Norcold on 24/7 and never had a problem, battery charged by TV when driving and when at occasional campsite with hook ups, have solar but seldom have needed it.

We have had our 2019 T@g Boondock Edge out for two weekend trips and I am still trying to figure out the battery and Norcold thing. First trip the battery looked dead when we got to our campsite but, it was just a disconnected terminal (came loose on the drive.) This past weekend we had shore power and I monitored the battery before we left the campsite. Checked the battery when we got back home after an hour and a half and the battery was at 12.1 so at 50%... Not sure what is going on, either the TV is not charging when we are driving or the 45 minutes in the driveway while we were washing it took the battery down that much? I would like to hear what or how others get so much from their battery. I have been monitoring it and we store in a garage where it is hooked up to power.

BBsGarage

@Nfallon said:

@tagurit said:
Same battery that came with our 2017 T@G and still there. Did at least 12,000 miles last year including one 24 day trip with the Norcold on 24/7 and never had a problem, battery charged by TV when driving and when at occasional campsite with hook ups, have solar but seldom have needed it.

We have had our 2019 T@g Boondock Edge out for two weekend trips and I am still trying to figure out the battery and Norcold thing. First trip the battery looked dead when we got to our campsite but, it was just a disconnected terminal (came loose on the drive.) This past weekend we had shore power and I monitored the battery before we left the campsite. Checked the battery when we got back home after an hour and a half and the battery was at 12.1 so at 50%... Not sure what is going on, either the TV is not charging when we are driving or the 45 minutes in the driveway while we were washing it took the battery down that much? I would like to hear what or how others get so much from their battery. I have been monitoring it and we store in a garage where it is hooked up to power.

Start by checking pin 7 (the +12v charging line) on the TV to make sure you have power there.

Nfallon

This is where my knowledge goes south. Wouldn’t I have power if all my lights work, brake, blinkers? How do I check to see if I have power?

McNutty195

Not necessarily. If there is something wrong with either your cord or the wiring than you could be getting a good connection in the other 6 pins (lights, brake, blinkers etc.) but not pin 7 which is the one that charges the battery.

BBsGarage

Or the charge line is not installed. It's usually a separate fused wire from the battery or relayed off of the battery.
If you do not have a multi-meter or some other way to see if the pin is live, you can get one of these.

https://www.amazon.com/Vehicle-Trailer-Wiring-Circuit-Tester/dp/B0066CGLS6

Sharon_is_SAM

The easiest way to tell if you have a charge line without using any meters. (This method does not tell you how efficient it is).

Turn off your TaG battery by disconnecting the negative, turning off the battery cutoff switch, or removing the fuse at the battery.

Hook your TaG to the 7-pin, crank the TV engine. Turn on an interior light in the TaG. If it comes on, you have a charge line. Turn off the engine, if the light goes out, you have an isolation relay in your TV. If the light stays on, you do not have an isolation relay.

Hope this helps,

Sharon

BBsGarage

@Sharon_is_SAM That works too, but how is a guy supposed to stock up on gadgets doing it that way?

tagurit

I believe you either have a short somewhere or a bad battery if you lost half your charge in 90 minutes on the road.

Sharon_is_SAM

@BBsGarage, well, I saved you some room for some bigger, more expensive gadgets🤑.

Nfallon

Thank you everyone, looks like I have some investigating to do. Y’all are the best.

Sharon_is_SAM

@Nfallon, you said you were on shorepower and you were monitoring your battery. How were you monitoring it and did you check the voltage with the battery isolated from shorepower?

Nfallon

@Sharon_is_SAM, I have unplugged and waited about 30 minutes to be sure that I got a correct reading with an adapter that plugs into the cigarette outlet with the USB ports. I don’t keep it plugged in as the light drives us crazy.