Temperature Sensors In Parallel Connection

No!

Well actually you can do this. Nothing will explode, or be damaged in any fashion by connecting these two sensors together in parallel. You just won't have any useful information from doing this. A NTC thermistor means that the resistance will decrease as the temperature increases. By connecting the two thermistors in parallel you will immediately make the electronics record an extremely hot temperature condition. If this thermistor is part of a feedback system then you may damage something though.

Now if (and a very big if) the electronics recording range, the nominal expected temperature and the nominal resistance of each thermistor happens to put everything in the correct range with the two thermistors wired in parallel then this is possible. However, to do this properly you'd need to have a good understanding of circuit theory, particularly Kirchoff's laws and Norton's mesh analysis to assure a working system. If you already understood this, then you wouldn't be asking this question.

If the thermistors are of the same type, you may get away with it by getting two more, and putting them in series with the existing ones, then connecting the two pairs in parallel (giving the same overall resistance as one thermistor when all at the same temperature.

But it's a very big "may"; there's no saying how well the charging process would be controlled without a detailed analysis of the charging circuit, batteries etc.

Don't do it!!!

For all the reasons already explained, plus since they are in parallel and the resistance will be split, the apparent temperature would be some sort of "average" of the two.

You could have one hot spot (boiling) and one ordinary and the output would indicate an apparently safe temperature.

Just do a Boolean table of some possible temperature states for the sytyem and you will see that the results will be meaningless. (That is multiple input conditions will give the same output signal.)

If you have only one reader, then multiplex the thermisters and read tehm independantly.

"You could have one hot spot (boiling) and one ordinary and the output would indicate an apparently safe temperature.".

I thought this one through, but as their resistance decreases with increasing temperature, the parallel combination resistance will be dominated by the lower resistance at the hot-spot^[1], so it would control to safety. It wouldn't, however, necessarily do much good charging the two banks optimally.

Also, monitoring the voltage of and current into each bank would be some kind of horrible average or somesuch.

Good thought about multiplexing, but it would need a pretty special controller - probably cheaper (and safer) to just get two controllers.

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[1] my "series-parallel combination" assumes that the two thermistors in each leg (i.e. in each bank) are both heated by the batteries.

For any battery bank a single thermistor is useless (going from your previous posts these are large scale units).

If you're going to be doing this seriously each cell needs to be monitored. While the ambient temperature of a bank seems OK, one cell could be boiling away unnoticed.

To my mind you need to rethink the whole scenario.

In modern times you let an inexpensive microprocessor collect and collate many measurements for you. If all are ok, fine. If not dig down. The data is there.

Thanks friends for the information, I think the best is to have 2 controllers, 1 for each battery bank and then connecting to the load bus in parallel.