Tomb8764 Posted January 31 Share Posted January 31 Hey everyone, so basically I can't get my '71 RL700L to start as of now. It will not crank over, when I try you can hear the series parallel switch make a loud click. Also not sure if it is connected or not, but I've also developed a short that won't allow me to turn off the lights. Unfortunately but not surprising this truck has had lots of backyard wiring done, so I'm not sure how everything is connected. Also the S/P switch isn't very old replaced it about a year or more ago. Thanks Tom Quote Link to comment Share on other sites More sharing options...
Freightrain Posted February 1 Share Posted February 1 What batteries are you running? Four 6s or a couple 12v? Are they good? Are the cables and ends good? Is the starter good? Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
Tomb8764 Posted February 1 Author Share Posted February 1 4 6s. They all tested good. Started up fine about a month ago. Quote Link to comment Share on other sites More sharing options...
Tomb8764 Posted February 1 Author Share Posted February 1 Also replaced cables about a year ago Quote Link to comment Share on other sites More sharing options...
hicrop10 Posted February 1 Share Posted February 1 Did you try tapping the s/p switch with a hammer? It may be stuck. 1 Quote Link to comment Share on other sites More sharing options...
Tomb8764 Posted February 2 Author Share Posted February 2 hicrop10, that is something I haven't tried. Maybe tomorrow I'll give it some taps and see how it goes. Thanks Quote Link to comment Share on other sites More sharing options...
70mackMB Posted February 2 Share Posted February 2 l'm only allowed to use a very small hammer when it comes time for problem solving. .....Hippy 2 Quote Link to comment Share on other sites More sharing options...
Freightrain Posted February 2 Share Posted February 2 If you here it "clunk", then maybe the contacts are crusty? You can take the S/P switch apart and clean the contacts(two big washers). I used to dismantle mine in a regular occasion back when I still have one. I removed it the next summer and went 12v starter and alt. 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
Tomb8764 Posted February 3 Author Share Posted February 3 Well I lightly beat on the SP switch with no luck. So I went back through and checked all the batts again and found 1 of the 4 is junk, it won't hold above 4v and under a load is nothing. So I'll be replacing a battery (maybe 2), if that fails I'll open up that SP switch for further exploration. Quote Link to comment Share on other sites More sharing options...
Brian L Blaylock Posted February 3 Share Posted February 3 If you’re using 4 6 volt batteries do yourself a favor and replace all 4 of them 2 Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted February 3 Share Posted February 3 I don't know if you can still get them, but before I spent a lot of money on that system, I would look into a 24 volt Maxwell ESM. Keeps the 24 volt cranking and cables, allows you to use the two best 6 volts for the rest of the 12 volt system, and Maxwell will recharge off the 12 volts. Not cheap, but if you are planning to change to 12 volt, you have to change the starter and cables, plus a set of 12 volt batteries, that makes the Maxwell more competitive. Quote Link to comment Share on other sites More sharing options...
Tomb8764 Posted February 6 Author Share Posted February 6 Thanks for the suggestion Geoff, but the maxwell esm is a bit rich for my blood. Looks like a good system though. I'm sure it will bite me in the butt later, but I'm probably just going to replace the one pair of batteries and see if it fixes my problem. Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted February 6 Share Posted February 6 Something to remember is that you can't properly charge batteries in parallel Maybe just try charging a battery at a time or just two in series if you only have a 12 volt charger Paul Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted February 6 Share Posted February 6 No, it is the other way around, you can't be sure of bringing cells in series to an equal charge. All batteries in parallel "see" the same voltage, but those in series are dependent on those below and above them in the stack. In an ideal world, you would charge each cell of a battery individually, then place them in series for the work needed. That, of course is not practical, so we charge them in groups of 3 or 6. The reason they say don't just replace one battery in a series group, is it's condition will be effected by all the other in the series group. In other words, the weakest link in the chain will determine how strong the chain. Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted February 6 Share Posted February 6 11 hours ago, Tomb8764 said: Thanks for the suggestion Geoff, but the maxwell esm is a bit rich for my blood. Looks like a good system though. I'm sure it will bite me in the butt later, but I'm probably just going to replace the one pair of batteries and see if it fixes my problem. Yes, it is a hard sell to make, BUT, as I said, if you are considering replacing your 24 volt start/ 12 volt run with a full 12 volt system, you are going to need new cables, new starter and likely new batteries. Add up all that, and the cost of only the Maxwell unit isn't as dear as it first looks. I can attest to the advantages, having a 12 volt unit, the 24 volt would only increase those advantages. Hard to justify on a "hobby" truck, more easy to on one that is out earning its keep daily. Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted February 6 Share Posted February 6 4 hours ago, Geoff Weeks said: No, it is the other way around, you can't be sure of bringing cells in series to an equal charge. All batteries in parallel "see" the same voltage, but those in series are dependent on those below and above them in the stack. Your incorrect Geoff In parrallel the current will flow to thru battery of least resistance on charging which is the highest charge battery The battery with the lowest charge slowly gets further abd further discharged until it's no longer serviceable Anyway I offer my advice and that's all it is, advice There's a good reason why almost everything we use has batteries in series and not in parallel From our mobile phone to the Tesla cars the hipsters drive today Paul Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted February 6 Share Posted February 6 (edited) Paul I will have to disagree, not about the least resistance, but the state of charge in the battery. With the way they are charged in parallel, all the batteries see the same charge voltage, the current will flow to each as they all charge, the current may vary on how it is divided, but all will be raised to the same voltage. On in the pack that had a bad cell would get hot, and the current draw wouldn't taper to zero, but the other batteries in the pack will fully recharge. As for charging in series, it limits to all in the string. Li batteries and super capacitors are monitored and balanced individually even while being charged in series, to prevent damage from cell imbalance. It was not possible in days gone by and not economic with systems like trucks to have an active battery management system, but it would benefit from one. It is precisely why 24 volt start 12 volt run, just don't leave all the batteries in series and pull the 12 volt load off the tie between the batteries ( battery balancers or dual output alternators are used). Edited February 6 by Geoff Weeks Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted February 6 Share Posted February 6 The issue/question is NOT will one bad battery pull the others down, it will in both cases, The question was if replacing just one, will it damage the others, and there the answer is no, but all will be better in a parallel bank than a series bank after the bad battery is replaced. A series will be held to the capacity of the weakest battery Lets say you put an 8D and a lawn tractor battery together to crank a diesel, In parallel, you get the full current of the 8D and a little help from the lawn tractor battery, in series you are limited to what the lawn tractor battery can pass. Quote Link to comment Share on other sites More sharing options...
Tomb8764 Posted February 6 Author Share Posted February 6 Thanks for all the information Geoff and Paul. Quote Link to comment Share on other sites More sharing options...
mowerman Posted February 13 Share Posted February 13 Quote Link to comment Share on other sites More sharing options...
mowerman Posted February 13 Share Posted February 13 i had a couple of them rebuilt but that was over 40 years ago....seems thier still available hope this helps....i wound up going to air start on mine ...i had a similar issue...bob Quote Link to comment Share on other sites More sharing options...
Popular Post Tomb8764 Posted February 13 Author Popular Post Share Posted February 13 Thanks Bob, That is a way better price than my local source. I was quoted $250+ for a new switch. I finally solved my issue for now. The s/p switch was fine. I purchased a single new 6v battery(I know should have done a pair). Chased down some bad wires. Got it fired up today and it runs like a dream. Thanks for all the help everyone. 4 1 1 Quote Link to comment Share on other sites More sharing options...
mowerman Posted February 14 Share Posted February 14 Excellent yeah sometimes it pays the shop around a little bit… bob Quote Link to comment Share on other sites More sharing options...
mowerman Posted February 14 Share Posted February 14 Yeah, batteries are a fortune but I have also heard that and most cases of four have to match …. Bob 1 Quote Link to comment Share on other sites More sharing options...
Solution mrsmackpaul Posted February 14 Solution Share Posted February 14 You can bung a amp gauge on each bank and just monitor that each side is charging Anyway the main thing is your up and running fine now But to stop a battery failing in the future the batteries need to be monitored for charge as regularly as checking your oil and water A hydrometer can be used once a week There are other methods but this is quick and simple and accurate way to monitor the batteries Paul 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.