Checking batteries

Topic: Checking batteries (Read 1709 times) previous topic - next topic

Checking batteries

April 25, 2015, 11:35:29 am

I've finally got a day with decent weather and some time to work.

The plan is to raise the rear of the coach as far as it can go, then disconnect the negative terminal of one of the two house batteries. While I'm trying to figure out where those batteries are grounded, that one battery should be out of the charging circuit. If that battery has a problem, I should see a voltage drop in a couple of hours. If I don't see any voltage drop I'll put that one back into the circuit and disconnect the other one. In the meantime I still have one battery in the charging circuit and I can use lights, pump, etc. Does my thinking make sense?

Re: Checking batteries

Reply #1 – April 25, 2015, 12:08:13 pm

David,

In reading your post, do you suspect you have a house battery that is not grounded? You could pull the positive terminal and then using a voltmeter, check the voltage at the battery post going to the chassis for a ground point.

Never a bad idea to run an extra short ground cable between the negative terminal and the closest frame location you can easily reach. Same with engine batteries.

Piece

Re: Checking batteries

Reply #2 – April 25, 2015, 12:18:08 pm

Actually, I'm not sure what is going on. I'm thinking that maybe the house battery bank ground may be bad, or maybe one of the house batteries is bad. Since both house batteries are a year old I'm hoping that that isn't the case.

My idea is to isolate (disconnect) only one of the two house batteries at a time. That way I still have a battery into which the converter/charger is putting electrons and therefore I can still run the 12v stuff. Does this make sense?

Re: Checking batteries

Reply #3 – April 25, 2015, 03:05:33 pm

Please tell me the negative cable from the house batteries doesn't end behind/underneath the starter!

A couple of people have suggested that I run a new ground cable from the batteries to a convenient grounding point. Would any convenient bolt on the engine or transmission be suitable for this? I'm sorely tempted to pick up a length of cable and some terminals tomorrow after church. There is a bolt that is just holding the pan on with nothing around it, and if that would work I'll use it.

Does each battery have a separate cable going from negative to ground?

Re: Checking batteries

Reply #4 – April 25, 2015, 03:24:04 pm

David,

You definitely want a good large-gauge ground direct to the starter or very near it. You ALSO want a good ground to chassis clean metal and also to any other high amp device such as jack motor.

Electrons have to travel ROUND-TRIP to provide power, A good positive connection is NOT enough.

Said another way, can't have too many good grounds. Adding is fine. BUT, do not connect one to a bolt that will direct electrical power to an area where you don't want it. Not sure a pan bolt would be a good ground location.

Re: Checking batteries

Reply #5 – April 25, 2015, 03:28:34 pm

Thanks, Brett. I'm looking for a good place to run another ground wire that is fairly close to the house batteries and is clear of moving parts and not in the way of something else that will eventually need attention. I understand that drilling into the frame is not a good idea, which is why I'm looking for an existing bolt that can be used.

I think I found a possible candidate. There is a bracket that holds one of the hydraulic oil reservoirs that has some extra holes in it. There is some paint on the bracket, but that can be removed easily. The bracket itself is attached to the frame. A 10' length of cable will reach very easily. My plan, unless someone has a better one, is to get 10' of battery cable and attach one end to the negative terminal of the lower battery. That terminal has only two wires on it, whereas the upper one has three. The other end will be attached to the bracket, and cable ties will be used to keep the new cable away from other things.

Re: Checking batteries

Reply #6 – April 25, 2015, 03:43:36 pm

Brett makes several good points. While batteries need a good ground to the chassis, the engine must also be well grounded. I have seen several vehicles with good chassis grounds but broken or poor engine grounds. Agree, engine pan bolts might not be a good location. Many vehicles place a ground cable under the fastener that bolts the starter to the engine. This way, the engine battery ground is close to the starter.

I like to use welding cable and copper lugs with the proper sized hole for the bolt that goes through it. Then I strip the cable back and use a torch or gas stove to heat the copper lug and then using electrical solder, solder it on. You can slide shrink tubing on before you solder and then slide it down to cover the cable/lug joint and heat it so it shrinks and makes a nice clean installation.

Pierce

Re: Checking batteries

Reply #7 – April 25, 2015, 03:51:53 pm

If your plan is to isolate a bad battery I would suggest that you buy a load tester. Disconnect all cables from each battery, test each battery separately and then you have a starting place. If battery is bad or charge on adjacent batteries is uneven then replace them and at the same time verify all connections.
Gary B

Re: Checking batteries

Reply #8 – April 25, 2015, 04:06:35 pm

Hmmm, another tool. Might have to check that out tomorrow when I try to buy a cable and ends. Pierce, your plan is what I had in mind. Just thought of something - don't know if I have a propane torch yet or not. If not I'm sure that one of the other guys here has one.

Re: Checking batteries

Reply #9 – April 25, 2015, 05:12:46 pm

Yes, I agree with Gary, load testing the batteries is really the only reliable way to check them. To properly test an 8D 1400 CCA RV battery requires a heavier load tester than you'll find at NAPA or O'Reillys. Here is the Auto Meter 800 amp tester. I'm not sure how long this sale will last, usually these are about $600 new.

Auto Meter 800 Amp Load Tester

I bought one of these on eBay for $75 and all it needed was a good cleaning. (The DW says I am obsessive/compulsive, I have 2 of these from eBay now - the second one needed new meters)

Re: Checking batteries

Reply #10 – April 25, 2015, 07:05:19 pm

Several of you have mentioned adding large gauge wire as an extra ground. How large are you talking about?

I picked up some 3/0 and some 2/0 from Home Depot and Lowe's (end of the roll at 25% to 50% off). I also have some #2 that I used when adding a subpanel to install my 50 amp outlet.

Additionally, I have a lot 6/3 +G that I was going to use to rewire for the RV. Could I use the 6/3 as a thicker gauge by soldering all the wires at each end together? Oops, just realized that it might not be stranded wire ...?

I know, I know; I have the diploma, but that does not count for much in the practical application of wire gauges in an RV.

Would some kind soul please help a veteran out here?

Thanks,

Trent

Re: Checking batteries

Reply #11 – April 27, 2015, 05:40:54 pm

Quote from: prfleming – April 25, 2015, 05:12:46 pm

Yes, I agree with Gary, load testing the batteries is really the only reliable way to check them. To properly test an 8D 1400 CCA RV battery requires a heavier load tester than you'll find at NAPA or O'Reillys. Here is the Auto Meter 800 amp tester. I'm not sure how long this sale will last, usually these are about $600 new.

Auto Meter 800 Amp Load Tester

I bought one of these on eBay for $75 and all it needed was a good cleaning. (The DW says I am obsessive/compulsive, I have 2 of these from eBay now - the second one needed new meters)

Well I purchased this meter from the above web site and thought the advertised price was to good to be true. I was just notified my order was cancelled and I was given a full refund.

Re: Checking batteries

Reply #12 – April 27, 2015, 06:43:16 pm

We carry the Mac BT8300 Battery Tester, find it very dependable and displays the Battery CCA remainng capacity etc.. It is he same as the OTC tool listed on Amazon. No idea if it works on AGM or Gel types.

Re: Checking batteries

Reply #13 – April 27, 2015, 07:22:27 pm

OTC Tools and Equipment shows to be National Tool Wearhouse on Amazon. They show the same Auto Meter 800 Amp Variable Load Carbon Pile Tester for $580.24.

NTX Tools & Tools For You appear to be operated by Coastal Tool Supply LLC. They are advertising the same Auto Meter 800 Amp Variable Load Carbon Pile Tester for $118.75. I was advised by Coastal Tool, through PayPal, that the order was cancelled due to a pricing issue. However both web pages are still advertising it at this price.

Re: Checking batteries

Reply #14 – April 27, 2015, 07:42:49 pm

Quote from: Dave M – April 27, 2015, 06:43:16 pm

We carry the Mac BT8300 Battery Tester, find it very dependable and displays the Battery CCA remainng capacity etc.. It is he same as the OTC tool listed on Amazon. No idea if it works on AGM or Gel types.

The OTC 3183 Is not accurate for AGM batteries. For AGM batteries, you will need the OTC 3167 Sabre HP. I found this out after buying the OTC 3183. I now have both, the OTC 3183 and the OTC 3167 Sabre HP.

Re: Checking batteries

Reply #15 – April 27, 2015, 08:25:19 pm

Quote from: Dick Henry – April 27, 2015, 07:22:27 pm

OTC Tools and Equipment shows to be National Tool Wearhouse on Amazon.

OTC tools is owned by SPX and a part of Bosch Automotive Services Solutions Division.

Re: Checking batteries

Reply #16 – April 27, 2015, 09:35:19 pm

Quote from: Dick Henry – April 27, 2015, 05:40:54 pm

Well I purchased this meter from the above web site and thought the advertised price was to good to be true. I was just notified my order was cancelled and I was given a full refund. :'(

Yea, I wondered about that ad. If you're not in a hurry, watch eBay. I have bought 2 that way. Repair parts are available from Auto Meter. I have a saved search with an alert for these. I promise to not bid on the next good deal! ;)

With a quick search I found this, looks like the meters are not broken, maybe he will take an offer:

800 Amp Load Tester

Here is a competitor - not sure of the quality compared to Auto Meter (probably made in China):

1000 Amp Load Tester

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Checking batteries

Reply #17 – April 27, 2015, 10:03:31 pm

Hi Guys,

Harbor Freight sells a carbon pile load tester:

500 Amp Carbon Pile Load Tester

I have one, it works quite well on my AG8Ds.

Jim

Re: Checking batteries

Reply #18 – April 27, 2015, 10:28:55 pm

Jim, yes these 500 amp units are available for cheap (I have a 500 amp tester also.) But, to fully test a 1400 CCA 8D starting battery, you need to pull some heavy duty current and draw approx 700 amps continuously for 15 seconds. The 500 amp tester will tell you if you have a battery with a severely degraded cell and is capable of testing your alternator output under various loads.

Re: Checking batteries

Reply #19 – April 28, 2015, 01:12:23 pm

Quote from: Dick Henry – April 27, 2015, 05:40:54 pm

Well I purchased this meter from the above web site and thought the advertised price was to good to be true. I was just notified my order was cancelled and I was given a full refund.

I ordered one from them before I saw this post so I called them to see if they had my order. They said yes and it was going out today. I mentioned about the cancellation of someone who has already ordered. She said she had no idea why because they have many in stock. After I hung up she called back and apologized that her price is over $400. I said why do you not correct the website price and she said "IT" is slow and had something to do with Google. So she said I was not charged because it was not shipped.

Re: Checking batteries

Reply #20 – April 28, 2015, 01:32:35 pm

Looks like lot of negatives on Google about NTX.

Re: Checking batteries

Reply #21 – April 28, 2015, 01:59:34 pm

USA Tool Wearhouse has the same price as Tools for You. Both of these companies appear to get their merchandise from Coastal Tool Supply LLC. At least that's where my PayPal refund came from. I have sent an email asking why the web pricing hasn't been changed and why have I not heard from someone in the company about the price discrepancy. My phone number and email address are on the order. If it wasn't for PayPal I would still be wondering. Reminds me of a car dealer pricing a car that they don't have to get you in the door. I wonder what else they have advertised that they won't sell.

Re: Checking batteries

Reply #22 – April 28, 2015, 02:20:23 pm

Well I just received a rapid response from USA Tool Wearhouse. I'm impressed. Also Tools for You has changed their price on their web site to $510.03

Dick,
The price has been changed, We made a mistake and had to cancel the order. Your were set for a phone call by days end today. Sometimes mistakes are made and we have to act fast to protect the customer to make sure they get their money in a timely manor. While I would love to be able to call everyone right away. We are busy today and wanted to make sure you saw refund and then would get a call with explaintion later today
Thank you for your understanding

Regards
Allen Dimick

Re: Checking batteries

Reply #23 – April 29, 2015, 08:54:07 am

Dick,

Proves the old adages: "Perseverance Pays Off" and "The Squeaky Wheel Gets The Grease". (Sorry you didn't get the "bargain" tester.)

Re: Checking batteries

Reply #24 – April 29, 2015, 09:01:47 pm

I bought 10' of battery cable and connected one end to the negative terminal of the lower battery and the other end to a freshly cleaned bracket that is attached to the frame. The negative terminal I used had three cables on it, while the other one already had four. One of those connections, of course, connects the two batteries to each other. I could have gotten away with less cable, but I wanted to have enough in case I need to try another connection point.

I tried cranking the generator. As before, all I got was a lot of clicking. The lights in the coach were blinking in time to the clicking. I can see the generator trying to turn. Also as before, a few minutes after I came in the house lights dimmed and the Kool-O-Matic fan slowed down. A few seconds later all was back to normal. All of this was done while connected to 50A service.

Conclusions so far: All connections that I can see seem to be fine. I'm quite certain that I have a good ground for the house batteries. The batteries themselves seem to be fine.

Further questions and tests: Friday I'm going to shut down all the 120V stuff (computer, tv) and flip the breaker. IF the interior lights stay on I'll try starting the generator. I'm pretty sure it won't start, but if the lights stay on then I'll know the batteries are good.

As I was writing this Jo Ann and I tried to remember when the last time the generator worked. We're pretty sure it was working when we headed to Pevely in October and wasn't working when we left there on 1 December. Question: is it possible that the generator starter is the culprit? It is turning the engine, but not fast enough to fire.

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